Air conditioning system

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Air conditioning

Index Subject Page History of air con systems 5 Heat sources 6 Temperatures inside a vehicle 7 Solution cooling 8 Heat definition 9 Heat transfer 10 States of aggregation 11 Latent heat of evaporation 12 Temperature and pressure 13 AC operating principle 15 Refrigerant R12 17 Ozone hole 18 Role of ozone 19 Green house effect 20 Refrigerant HFC- 134 a 21 Refrigerant properties 22 Pressure and boiling point 23 Required changes for R 12 replacement 24 System modifications 25 AC system overview 26 Refrigerant properties 27 Swash plate compressor 30 Variable swash plate compressor 31 AC low load condition 32 AC high load condition 33 Operation diagram 34 Scroll type compressor 35 Compressor clutch 38 Hose structure 38 Condenser 40 Dryer 41 Expansion valve 42 CCOT refrigerant cycle and components 43 Expansion valve inner equalizing 45 Expansion valve external equalizing 46 Evaporator 47 Refrigerant flow control 48

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Index Subject Page AC operation cycle 49 Heater unit 50 Electric circuit 51 Dual pressure switch 52 Triple pressure switch 53 APT sensor 54 Multi speed fan PWM control 55 Cooling fan control 56 Thermostatic switch 57 Fin sensor / thermistor 58 Blower motor speed control 59 Maintenance and trouble shooting 60 Pollen filter 61 Safety precautions 62 Preliminary checks 63 Bad smell 65 Leak detector and leak test 66 Basic gauge set 69 Performance check 71 Discharging and adding of refrigerant 72 System evaluation by pressure gauges 73 Special tools 82 Disassembly of clutch and pulley 83 Air gap measurement 84 Pressure relief valve 85 Oil specifications and level adjustment 86 Hose and pipe connections 88 FATC system / AC control 89 AC control signals 90 Component location 91 HVAC unit 92 Controller types according to system / Temp unit change 93 Switch functions 97 Control logic / CELO function 98 In-car temperature sensor 99 Photo sensor 100

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Index Subject Page Air quality sensor 101 Water temperature sensor 102 Humidity sensor 103 Ambient temperature sensor 105 Blower motor speed control 106 Power transistor inspection 107 MOSFET 108 Intake door actuator 109 Mode door actuator 110 Temperature door actuators 111 PTC heater 112 PTC heater control 113 FATC diagnosis 115

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History Between 1940 and 1942, Packard equipped 1,500 automobiles with air conditioning. By 1954, about

36,000 cars had factory-installed air conditioning systems. In 1966, the Motor Service Manual states that 3,560,000 A/C units had been serviced in the U.S. Sales of A/C equipped cars soon took off. The 1987 figure for A/C units was 19,571,000. It's estimated that now over 80% of the cars and light trucks in operation have air conditioning.

Early automobiles were not exactly comfortable. In winter, passengers huddled under blankets and in the summer, air conditioning was a breeze that resulted from a top speed of 15 mph. In 1908 when car manufacturers began closing up the cabs on cars, heat soon became an issue. Vents were put in the floors of cars, but this brought in more dirt and dust than it did cool. A bucket of water near a floor vent was the first air-conditioning system. The temperature-reducing effect of air passing over water was called an All-Weather Eye. Such systems are actually still available for vans and RVs. This system was invented by Nash in 1938 and provided summer cooling and winter heating with a single knob. The first car with an actual cooling system was the 1940 model year Packard. The "cooling coil", a large evaporator, was located behind the seat, and the only control was a blower switch. This option allowed Packard to advertise, "Forget the heat this summer in the only air conditioned car in the world." The system was advertised as a "Weather Conditioner" and also filtered pollen and dust from the air. The Weather Conditioner could also transform into a heating system by adjusting damper controls located in the trunk. Between 1940 and 1942, Packard equipped 1,500 automobiles with air conditioning. By 1954, about 36,000 cars had factory-installed air conditioning systems. In 1966, the Motor Service Manual states that 3,560,000 A/C units had been serviced in the U.S. Sales of A/C equipped cars soon took off. The 1987 figure for A/C units was 19,571,000. It's estimated that now over 80% of the cars and light trucks in operation have air conditioning. Changes are constantly being made to accommodate new car designs, environmental issues, passenger comfort and safety. Today, few people will consider a new car that does not have air conditioning. Today, heating and air conditioning systems are very efficient. Modern Automatic Temperature Control set-ups are more dependable than the older vacuum and thermostatic creations. Computers also insure that both the passenger and driver stay comfortable.

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Heat sources

When a car is driven on the highway or even when only parked in the sun, heat enters the car from many sources. Direct sunlight radiates heat on the roof and body panels and through the glass area. Heat is radiated from the hot pavement and from the passengers. Engine heat is conducted from the firewall. Exhaust system heat is generated by the exhaust pipe, tail pipe, muffler and catalytic converter and this heat enters through the floor. All of these and other miscellaneous heat sources increase the air temperature within the car. It has been noted that on a warm day (approximately 30°C), the interior temperature of a car left standing in the sun with windows closed can reach more than 60°C!

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Temperatures inside a vehicle An cooled down car interior does not only offer appropriate comfort, but is also basis for active driving safety .A super elevated interior temperature (in the summer frequently between 40 °C and up to 60 °C) worsens efficiency and perseverance, attention and response time of the driver. The result of this reaction delay is longer stopping distances and more accidents. Active safety is the most important benefit!

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Solution: cooling

Apart from air-conditioning (cooling) the interior, straight in the summer, an air conditioning system helps to provide clear view in the winter or on wet-cold days as it removes moisture from the air and thereby prevents fogging. Also it cleans interior air of pollutants. The strong pollution of air - in particular in heavy city traffic - arises also, by the usual ventilation system, in the interior of the vehicle. This impairment of the passengers is prevented by an air conditioning system through filters (they are also available w/o air-conditioning) and the cleaning from dust due to moisture removal.

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Heat definition

In order to understand the working principle of an air conditioning system it is important to understand the physical principles which make this system work. Heat in the correct amount will provide life and comfort. Heat in either extreme too much or too little, brings about uncomfortable situations. The control of heat means the control of comfort. Air conditioning is a way of controlling heat. To understand how an air conditioning system works, we must first understand the nature of heat. That seems a bit difficult to understand at first, but the principles of rising temperatures, evaporation, expansion and radiation will all become clear as we continue through this chapter. All substances contain heat. Sometimes they feel hot when they are substantially warmer than our own body temperature. Temperature is sensible heat. When something contains much less heat than your body, we say it feels cold. Cold is merely the removal of some heat. Heat will always travel from the warmer side to the colder. This process cannot be stopped. It can only be slowed down by insulation. Therefore: the air con system is not producing cold, but removing heat. In accordance with Natural Law, heat will always move from the hotter object to the colder one. Whenever there is a temperature difference between two objects, the heat energy will be transferred from the warmer object to the cooler one until both objects have stabilized at the same temperature. Examples: when you step outside on a cold day, you feel the cold. Not because the cold enters your body, but because heat is moving away from your body to the cold air, causing you to feel cold. The reverse is true when you are in a place which is warmer than your body temperature- you feel warmer because heat from the warmer air is moving into your body.

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Heat transfer

Conduction: heat travels through a substance, from a point of heat to a cooler area by conduction. We have all experienced this by lifting a hot pan from the stove. The handle is hot even though it is not in direct contact with the burner. The heat is conducted through the metal of the pan to the cooler handle. (Remember, heat moves from a warmer object to a cooler one). Similarly, a metal bar heated at one end will become hot at the other by conduction. Radiation: heat is radiated from any hot substance in the form of heat waves. These waves are a form of energy, and they will increase the temperature of any object with which they come in contact. The sun is the major source of heat for the earth. Its heat waves are transmitted through space and they heat up the earth as they come in contact with it. Direct sunlight is a good example of heat by radiation. Color has an important part to play in heat radiation. A dark colored vehicle will get hotter than a light colored vehicle. This is because lighter coolers reflect more heat (light) waves, while darker colors absorb more heat (light) waves. To put radiation heat in the perspective of an air conditioning system, note that the condenser, which bears the high temperature refrigerant, will conduct and radiate heat to the cooler outside air. Convection: heat is also conveyed (carried) from one point to another by the movement of a heated substance. This heat movement is called convection. When we turn on a hot water faucet, we get hot water, although the water heater is some distance away. This is because the moving water carries the heat from the water heater to the faucet.

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States of aggregation

Change of State: Evaporation and Condensation. A further effect by heat exchange is that the molecules may change their state instead of their temperature. At a certain point (boiling point, solidification point), e.g. water is transformed into steam or into ice. There are three processes which describe a change of state: Evaporation, Condensation, and Freezing Evaporation is the term used when enough heat is added to change a liquid substance to a vapor (gas). You are familiar with boiling water and the vapor (steam) that is given off. At the boiling point of water (100°C), enough heat is absorbed by the water to change its state. The liquid becomes a vapor. Condensation is the term used to describe the reverse of the evaporation process. If you take a vapor and remove enough heat from it, a change of state will occur which causes the vapor to become liquid. Freezing results when heat is continually removed from a liquid substance until it becomes solid. Remember that everything above –273°C contains some amount of heat. In an air conditioning system, freezing is a hazard to be avoided. NOTE: Plasma (ionized gas which has high electrical conductivity) is often considered as a fourth

state of aggregation.

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Latent heat of evaporation

Specific heat capacity Specific heat capacity is the quantity of heat in J (Joule) required raising the temperature of a substance. Specific heat capacity is a function of temperature. In the case of gases, it is necessary to differentiate between specific heat capacity at constant pressure and at constant volume. Specific heat of Fusion The specific heat of fusion of a solid is the quantity of heat in J required to transform1kg of a substance at fusion temperature from the solid to the liquid state. Latent Heat of Evaporation The latent heat of evaporation of a liquid is the heat quantity of heat in J required to evaporate 1kg of a liquid at boiling temperature. The latent heat of evaporation is highly dependent upon pressure. Example: When heat is added to a container holding 1 kg of water at 100°C (at sea level), the water will absorb 1023kJ of latent heat without any change in the thermometer reading. However, a change of state from liquid to vapor will occur. This heat that is absorbed is called „The latent heat of Evaporation. “ The vapor will retain the 1023kJ because they were required to cause the change of state. Latent Heat of Condensation When the above process is reversed and heat is removed from one kg of water vapor at 100°C (at sea level), the vapor will give off is 1023 kJ of heat without causing a drop in the thermometer reading. However a change of state from vapor to liquid will occur. This heat that is given off is called the „Latent Heat of Condensation. “

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Temperature and pressure

Heat Measurement The temperature or INTENSITY of heat is measured with a thermometer. While both Celsius (°C) and Fahrenheit (°F) are sometimes used, the majority of references in this manual will be to Celsius. A temperature reading tells us only the heat intensity or SENSIBLE HEAT of a substance and not the actual quantity of heat. The average person has a comfort zone of about 21-27°C. In this temperature range we feel the most comfortable.. As the temperature of anything is above or below this range, we think of it as hot or cold. Scientists tell us that a measurement called “Absolute Zero” is the point at which all heat is removed from an object. This point is determined to be –273°C.Any substance which is above this absolute temperature contains some heat. Understanding air conditioning necessitates also understanding pressure and the relation to temperature and constitution. The world we live in is surrounded by air or gas. Gas exerts pressure in all directions with equal force. The gas surrounding us is made up of 21% oxygen and 78% nitrogen. The remaining 1% is made up of other rare gases. This combination of gases is called atmosphere and extends some hundred kilometers above the earth and is held there by gravity. At sea level, the atmospheric pressure is 1.0bar and the boiling point of water is 100°C. If we were at a point higher than sea level, the atmospheric pressure would be lower and so would be the boiling point of water. If the pressure decreases to 0.38 bars, the boiling point of water will be 75°C. If the pressure decreases to 0.12 bars, the boiling point of water will be 50°C. If the boiling point of water is affected by a pressure drop, then it is likely that a pressure increase will also affect the boiling point of water. E.G. Steam cooker! Additional information: How to calculate Fahrenheit to Celsius and vice versa: C = 5/9 x (F-32) F = (9/5xC)+32 Kelvin = C +273 Rankine = F + 460

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Temperature and pressure

Pressure Heat Relation: it is important to know the pressure – temperature relationship of the refrigerant in the air- conditioning system. If the pressure of the refrigerant is low, its temperature will also be low. Inversely, if the pressure is high, its temperature will also be high. This means for example temperature increasing is pressure increasing and pressure increasing is temperature increasing. E.g. Air pump for bicycle, remembering this is important, because pressure change as well as temperature change is very important in the function of the A/C system.

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AC operating principle

In understanding the air conditioning system operation, we must introduce the components of the system and how they relate to one another. When we talk about the air conditioning system's basic components, we must also understand the terms High Side and Low Side of the system. The basic components of every air conditioning system will also be related to the High and Low side of the system. High Side: High side simply refers to that side of the system in which high pressure exists. It is the compressors job to create higher pressure (and higher temperature) so that the R134a will be able to condense and release heat at the condenser. A pressure differential is created at the expansion valve – beside the compressor it is the second dividing point between the high pressure and the low pressure side. Low side: Low side is the term used for that portion of the air conditioning system where low pressure and temperature exists. From the expansion valve, through the Evaporator and to the inlet side of the compressor, the R134a is in a low pressure state. This allows for heat to be transferred from inside the car to the colder R134a, and thus be carried away from the interior of the cabin.

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General An air conditioning system is removing heat from the outside air when it passes the evaporator, so that cool air is entering the compartment. The warm air inside transfers some heat to the colder air which just entered. By this the complete compartment is cooled. The pattern of the refrigerant cycle shows the operational principle of an air conditioning system: The refrigerant circulated in the closed cycle and constantly changes between liquid and gaseous condition. Thereby warmth is extracted from the interior and delivered outward. The refrigerant cycle essentially consists of five main components: Compressor, Condenser, Dryer / Collecting tank, Expansion valve, Evaporator. The components are connected to a closed refrigerant cycle, in which the refrigerant circulates. The refrigerant which enters the compressor is gaseous, and then it is compressed, by heat emission condensed, so that it becomes liquid. When reaching the expansion valve pressure reduction takes places, so that it is evaporated (within the evaporator) thereby taking up heat. As a gas it reaches the compressor again and the circle restarts. The refrigerant cycle is divided into a high pressure circuit and into a low pressure circuit (suction side). The points of separation are the compressor, the valve plate and the expansion valve.

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Refrigerant R12

As many of you know in the past the refrigerant which was used in cars was the so called R12. The reason to use it was the physical and chemical properties, such as the boiling point of – 28.9 degree Celsius. But it turned out that there were environmental problems such as ozone layer destruction. Therefore it was replaced with a new refrigerant: R134a

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Ozone hole

Theory of ozone layer depletion: Freon is an extremely stable substance, so it passes from the earth through the Troposphere and reaches the Stratosphere without breaking up. There, the diffused Freon is flooded with strong ultraviolet rays and broken up, releasing chlorine. With this chlorine as a catalyst, a reaction occurs, and the ozone is depleted. Once chlorine gets into the stratosphere, it remains there for a long time, and the ozone depletion continues. Control of CFC´s: In May of 1989, the “Vienna Treaty, Montreal Protocol First Treaty Powers Meeting“was held, and the proposal to strengthen regulations mandating the total abolition of specified Freon by the year 2000 was examined in detail. By this plan, the production of the target Freon would be reduced to 25% or less from January 1994, based on the actual results of Freon consumption in 1986. By the year 1996 they would be totally abolished. Ozone hole“phenomenon: Ultraviolet rays of a certain wavelength are harmful to living organism, are a cause of skin cancer, and exert an influence on genes. The ozone layer absorbs these ultraviolet rays, thereby performing an extremely important role in preserving life on earth. However, in 1985, Dr. Farman of Great Britain announced that a phenomenon can be seen over the South Pole, whereby the ozone layer is reduced in the spring and restored to the normal level in the summer. An artificial satellite sensor also captured this phenomenon, and the portrait which it sent revealed that the ozone in the sky over the continent of Antarctica was being depleted. Since this appears to be a hole in the ozone layer it was called the “ozone hole.” This “ozone hole” attracted the concern of scientists. The fact that the ozone layer was being depleted by Freon and there was a danger of harmful ultraviolet rays pouring onto the earth's surface had been pointed out more than 10 year's before. A decision was made to mount a large scale observation in order to investigate the mechanism of this ozone hole and to clarify its relationship with Freon.

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Role of ozone

Role of the Ozone layer: the atmosphere which envelops the surface of the earth is divided into a number of layers and the one closest to the earth is called the troposphere. In the troposphere, temperatures are highest near the surface to earth, and as the altitude increases, the temperature decreases. For this reason, convection occurs in the atmosphere and is manifested as atmospheric phenomena. In the 20 to 30 km altitude range of the stratosphere, the degree of concentration of ozone is high. This is called the Ozone layer. A certain wavelength of ultraviolet is damaging to living beings, is a source of skin cancer, and has an effect on the genetic structure. The ozone layer, by absorbing these ultraviolet rays, plays a critical part in preserving life on earth. Ozone formation: Oxygen atoms absorb ultraviolet rays and are broken up into oxygen atoms. These Oxygen atoms combine with oxygen molecules to form ozone. Ozone is formed near the equator where the amount of solar radiation is higher, and spreads in the direction of the poles through slow atmospheric movement.

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Green house effect

Greenhouse effect: as a result of the use of large quantities of fossil fuel (such as oil, coal and spontaneous gas), and the depletion of forests, the concentration of carbonic acid, freon, methane, etc. in the atmosphere is increasing, and the heat from the surface of the earth is being absorbed into the atmosphere. Under these conditions, it is said that this causes global warming.

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Refrigerant HFC-134 a

Specified refrigerants, chemically stable substances which are superior for heat resistance and non – combustibility, have the characteristics of being colorless and odorless without being inflammable, corrosive or toxic. For these reasons, they came to be used for a wide range of purposes such as refrigerants for air conditioners and refrigeration units, aerosol spray agents, cleaning agents for electronic systems, fire extinguisher materials, foam agents, and raw material for synthetic resins. On the contrary, the most important characteristic of an alternative Freon is that the Ozone depletion potential is small, and it is indispensable minimum condition is that it can be used safely in each area. Freon is a substance in which parts or all of the hydrogen atoms, such as methane and ethane, are rearranged into the halogen elements of fluorine (F) and chlorine (C l).By this combination; various kinds of Freon are being made. For an alternative substance which doesn't include chlorine, a source of ozone depletion, HFC134a is considered to be the most suitable substance, and testing of its safety with PAFT-1 [Program for Alternative Fluorocarbon Environmental Toxicity Testing] is progressing.

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Refrigerant properties

The molecular size of R134a is much smaller than that of R12. As a result we have a higher loss of refrigerant. An amount of 10% up to 15% per year can be normal! Beside that the different boiling point requires changes in the system layout such as adjustment of expansion valve etc. And also it is necessary to use different oil. Retrofit therefore requires changing some items, such as the drier and furthermore the system should be flushed 2-3 times to get the mineral oil out as much as possible (after removing it from the compressor etc.) Substitutes which can be used instead of 134a are another possibility, but may be difficult to get and also cause problems in servicing: therefore we do not recommend substitutes for 134a.

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Pressure and boiling point

The boiling point of a liquid is indicated in tables and always refers to the atmospheric pressure 1 bar. If the pressure over a liquid is changed, then also its boiling point changes. All homogeneous liquids hereby behave in agreement. In the vapor pressure diagram you can recognize that for example with continuous pressure and a reduction in temperature, the vapor becomes liquid (in the condenser) .By reducing the pressure, the refrigerant of the liquid changes into the vaporous condition (in the evaporator). The evaporation process is used by air conditioning systems in vehicles. It works with an easily simmering material, which we call refrigerants. The applied refrigerants are R-12, which simmers at -29.8°C and R-134a) which simmers at -26.5 °C. The indicated boiling points correspond to the boiling temperature at normal atmospheric pressure (760 Torr = 1013.25 millibar).

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Required changes for R 12 substitutes

R134a, which was developed as an alternative substance to R12, has the following characteristics compared with R12: The compatibility with the conventional lubricating oils (compressor oil) is bad. Its degree of water solubility is high and the swelling and permeability of the seal materials and hose materials is high. Since the new refrigerant R134a has properties and characteristics which are different from those of R12, changes had to be made accordingly. If R134a is filled into an R12 air conditioning system, problems such as compressor lock or refrigerant leakage will occur. For this reason countermeasures are being taken so that erroneous gas charging can not occur, this was made along with changes due to differences in properties and characteristics. The differences in characteristics are: The pressure and load becomes higher when the ambient temperature is high (causes poor cooling). The system was matched to this by increased efficiency, changed magnetic clutch and condenser, changed specifications such as set values for pressure switches, expansion valves etc. For after sales service: there is no interchangeability of refrigerant, oil and O-rings. For prevention of wrong pipe connection and wrong refrigerant charging the shape of pipes, joints, charging valves and service tools identification were changed. For the prevention of refrigerant being released into the atmosphere the melt bolts were abolished and pressure relief valves installed instead.

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System modifications

CONDENSER: Reduce condensing temperatures to maintain performance because R-134a system generally has larger condensing capacities than those designed for use with R-12. COMPRESSOR: H-NBR provides better compatibility with R-134a PAG. Compressors for use with R134a generally have been made durable to accommodate the higher pressures and different lubricants associated with the refrigerant. COMPRESSOR OIL: Mineral oil is not soluble with R-134a4. HOSE MATERIAL: Improved containment and soluble with R-134a DESICCANT: Materials changed diameter of pores changed for better absorption of moisture, quantity changed from 30 to 45g. HIGH PRESSURE CUT-OUT SWITCH: R-134a has higher discharge pressures than R-12 at same condensing temperature. CHARGING PORTS: Unique charging port of R-134a is provided to avoid confusion of R-12’s. Reduce leakage of system and prevent charging with the wrong refrigerant.

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AC system overview

In an air conditioner, the heat which was conducted into the refrigerant in the evaporator is conveyed through the system by the moving R134a (it is being moved by the pumping action of the compressor). This flow of refrigerant carries the heat from the evaporator to the condenser where it is given off to the atmosphere. Similarly, once the heat which was conveyed to the condenser is conducted through the condenser fins, it radiates to the atmosphere. Ram air flow (air passing through the condenser caused by the forward movement of the vehicle) carries away the heat from the area of the condenser. This is another form of convection. In the air conditioning system, heat from inside the car, is conducted through the metal fins of the evaporator and into the cooler refrigerant (R134a). Similarly, heat is conducted out of the warmer refrigerant at the other end of the A/C system, and through the metal fins of the condenser, where radiation and convection carry it away. As the heat is absorbed, the refrigerant vaporizes and carries the heat to the condenser. At this point the refrigerant is at high temperature and high pressure. The temperature of the refrigerant is higher than the outside air at the condenser. The heat again flows from the warmer to the colder object, and thus the heat is released outside the vehicle. By giving off heat the refrigerant condenses back to liquid and the cycle starts over again. One of the major advantages of using refrigerant is that it is able to cycle through its changes of state within a wide range of temperatures and pressures that exists within the A/C system. Reminder: Refrigerants go through a phase change twice in the cycle. From gas to liquid in the condenser and from liquid back to gas in the evaporator.

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Refrigerant properties

Enthalpy is the amount of energy that the refrigerant contains, and is measured in Kilo joule per kilogram of refrigerant. On this chart, constant pressure lines are horizontal, so if you move right or left the pressure stay the same while other properties change. Constant enthalpy lines are vertical, so if you move only up or down on the chart, the enthalpy remains constant, but other properties change. The lines of constant temperature in this diagram aren't straight, they follow a specific path. Note how the lines behave inside the so called wet dome, they are perfectly horizontal, which means that if the pressure and the temperature remains constant the mixture can be 0%gas, 100%gas or anything in between. The share depends on the enthalpy or in common words: how much energy is stored per kilogram refrigerant. Note that for a given pressure there is only one temperature where the refrigerant is saturated, which means that all refrigerant is just changed to gas. If the temperature is increased further it is called superheated. As the change of state equals to a change in enthalpy (amount of energy) it is the key for the air-conditioning function.

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1. Refrigerant enters the Compressor. In our example the cool gas has a temperature of 10°C at

about (2.2bar). 2. The compressor has done its job. Note that the pressure went from 2.2bar to about 13.5bar. Also

the temperature of the gas shot up to about 70°C. Along with the temperature and pressure increase, we have an increase in enthalpy (since we have moved to the right on the chart). The refrigerant now contains more energy and enters the condenser.

3. Once inside the condenser, the refrigerant gives up some of its heat the temperature went down but the pressure remained constant. The refrigerant here is saturated gas and now begins to condense as more energy is removed.

4. The mixture has a quality of 0%, it is a saturated liquid. The temperature of the refrigerant is the same as it was under point 3 but it now has far less enthalpy. This energy was dissipated through the condenser.

5. This point is the end of the condenser. Between points 4 and 5 the condenser is just cooling off the liquid. Note that the pressure remains the same, but both temperature and enthalpy are dropping. This process is called sub cooling.

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6. Between points 5 and 7 there is the expansion valve. As the refrigerant crosses through the expansion device, the pressure and temperature drops dramatically (note the vertical line on the diagram).At point 6 the refrigerant enters the wet dome area again.

7. We enter the evaporator. Note that some of the refrigerant is already a gas. According to the diagram we're at a quality of about 0.27, so the liquid /gas mixture is 27%gas. In this example, the refrigerant is about 0 C. This is the refrigerant begins absorbing heat, which is what we want it to do. Note the relatively low enthalpy. At this point the refrigerant is most of the way through the evaporator. It has absorbed a lot of heat note the enthalpy increase. Also the temperature of the refrigerant is the same as when it went into the evaporator. At point 8 the refrigerant is a saturated gas. When the refrigerant leaves the evaporator and enters the compressor at point 1, the temperature of the refrigerant increased somewhat. This is called superheat. Sub cooling and superheat: since the heat absorbing process takes places between points 7 and 1, this is called the refrigeration effect. If we could get more sub-cooling, we could move farther left on the chart, and then drop in to the wet dome at a point that would stretch the refrigeration effect. Also, superheat has a very valid purpose. Increasing the temperature of the refrigerant beyond the saturation point gives a safety factor against having some liquid refrigerant get sucked back in to the compressor. This could potentially happen if the refrigerant had not absorbed enough energy to turn completely to a gas. With the nature of automotive A/C systems, some form of capacity control is needed to ensure that the correct amount of cooling is provided for the load that's on the system (this will be explained in the next chapter). You won't need nearly as much cooling in April as you will in July. That being the case, the system must have some way of regulating itself.

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Swash plate compressor

Function (General) The compressor is driven by the engine. It increases the pressure of the evaporated refrigerant (gas), so that it is at high pressure (high temperature) and supplies it to the condenser. As the temperature decreases in the condenser the refrigerant becomes liquid. For the adjustment to different engine speeds, ambient temperatures or driver selected interior temperatures the delivery rate of the compressor is variable. Most compressors are varied in achievement by switching it on and off. In the swash plate compressor the pistons are moved by the so called swash plate, which is an plate connected to the shaft with an inclination. Therefore if the shaft turns the pistons are moved forward and backward (intake and compression stroke). Swash plate compressors have several independent pistons e.g. 5 pistons, which serve 10 cylinders. On the intake stroke the R134a, from the low pressure side of the system (from the evaporator) is drawn into the compressor. The intake of R134a occurs through a reed valve. This one way valve controls the flow of vaporous refrigerant into the cylinder. During the compression stroke, the vaporous R134a is compressed. This increases both the pressure and the temperature of the refrigerant. The outlet side (discharge) reed valves then open to allow the refrigerant to move to the condenser. From the outlet valve onwards the high pressure side of the system starts. NOTE: Compressors are designed to operate on refrigerant vapor only; liquid refrigerant in the

compressor would cause damage to the compressor reed valves. Some compressors have a so called thermo fuse installed into the solenoid coil to prevent belt damage in case compressor locks.

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Air conditioning

Variable swash plate compressor

Function The compressor is driven by the engine. It increases the pressure of the evaporated refrigerant (gas), so that it is at high pressure (high temperature) and supplies it to the condenser. As the temperature decreases in the condenser the refrigerant becomes liquid. For the adjustment to different engine speeds, ambient temperatures or driver selected interior temperatures the delivery rate of the compressor is variable. Most compressors are varied in achievement by switching it on and off. In the swash plate compressor the pistons are moved by the so called swash plate, which is an plate connected to the shaft with an inclination. Therefore if the shaft turns the pistons are moved forward and backward (intake and compression stroke). Swash plate compressors have several independent pistons e.g. 5 pistons, which serve 10 cylinders. On the intake stroke the R134a, from the low pressure side of the system (from the evaporator) is drawn into the compressor. The intake of R134a occurs through an reed valve. This one way valve controls the flow of vaporous refrigerant into the cylinder. During the compression stroke, the vaporous R134a is compressed. This increases both the pressure and the temperature of the refrigerant. The outlet side (discharge) reed valves then open to allow the refrigerant to move to the condenser. From the outlet valve onwards the high pressure side of the system starts. NOTE: Compressors are designed to operate on refrigerant vapor only; liquid refrigerant in the

compressor would cause damage to the compressor reed valves. Some compressors have a so called thermo fuse installed into the solenoid coil to prevent belt damage in case compressor locks.

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AC low load condition

If the cooling load is low the expansion valve is nearly closed. Thus the pressure in the inlet chamber is decreasing. If the pressure becomes lower than the standard value (2.0kgf/cm2) the diaphragm (which has a connection to the inlet chamber) is expanding and thereby opening the connection between the outlet chamber and the control chamber. Thus the pressure in the control chamber rises and the angle of the swash plate is reduced. This will reduce the delivery quantity to the required amount of refrigerant.

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AC high load condition

If the cooling load is high the expansion valve is nearly opened. Thus the pressure in the inlet chamber is increasing. If the pressure becomes higher than the standard value the diaphragm which has a connection to the inlet chamber is shrinking and thereby closing the connection between the outlet chamber and the control chamber. Thus the pressure in the control chamber decreases and the angle of the swash plate is increased. This will increase the delivery quantity to the required amount of refrigerant.

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Operation diagram

Here you can see the control strategy for the compressor. The control valve is connected to the inlet chamber of the compressor, to the outlet chamber and to the control chamber. The opening and closing pressure of the control valve is set mechanically by the balance of the inlet pressure, the outlet pressure and the springs inside of the valve. If the cooling load is low, the inclination angle (delivery quantity) is reduced. If the cooling load is high the angle and thereby the delivery quantity is increased.

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Scroll type compressor

The picture shows the scroll type compressor. On top of the compressor two sensors can be seen: one is a temperature sensor to detect the temperature of the refrigerant inside of the compressor, the other one is a speed detecting sensor, which recognizes the speed of the compressor. The compressor speed and the engine speed are compared by the belt lock controller. In the case the difference between them is to big (80 percent slip), the magnetic clutch will be deactivated. The belt lock controller is attached to the blower unit, just beside the intake actuator. This function is applied in order to avoid damage of the drive belt in the case that the compressor has an internal fault. The reason to do so is that only one drive belt is used for all the accessories such as water pump, power steering and alternator and air-conditioning compressor. This would result in the fact that if the compressor is locked and the belt gets damaged also the other devices are not operational anymore. Looking at the lower picture it can be recognized, that the shaft inside the compressor is slightly eccentric to the input shaft. Because of this the slider which transferring the movement of the pulley to the moving scrolls makes an eccentric motion. By this motion the scroll is moved from left to right and up and down. Due to these motion different sections between the two scrolls expand or shrink so that refrigerant is sucked in, compressed and discharged with higher pressure.

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As indicated one part is fixed in the compressor housing and remains stationery, while the other part is driven by the pulley (via the slider) and moves as described previously. The working cycle it is described on the next page.

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Operation cycle

Let’s have a look at the operation cycle of the scroll compressor. As this process is taking place continuously, so that several stages of refrigerant compression are reached at the same time we will follow the process for one process step by step. The process we will look at is marked in red, while other stages happening at the same time are colored different. Each color indicates the compression for one specific amount of refrigerant from intake to compression and discharge. The cycle starts when the ends of both scrolls open the intake, so that refrigerant can enter the gap. Let us define this position as 0° (rotation angle of the drive pulley). After 180° the moving scroll has changed the position in a way that the scrolls touch each other thereby closing the intake and building a chamber, so that no refrigerant can enter anymore, but also no refrigerant can escape. At the position of 360° the scroll reaches a position where the discharge port is closed and the size of the different chambers is reduced, so that the refrigerant is compressed. At the same time scroll is pushing the refrigerant into the direction of the discharge port. At 540° the refrigerant is compressed to the required level and leaves through the discharge port which is now open. At 720 degrees the scroll reaches the same condition, that it had at 0°, the circle restarts.

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Compressor clutch

The clutch consists of the solenoid coil, the pulley and the hub with clamp and feather/spring plate. The solenoid coil is fixed directly to the compressor housing and is located behind the pulley. The pulley is fixed to the compressor via a bearing and therefore can turn freely; the pulley is driven via a belt as soon as the engine turns. The hub is connected to the driveshaft of the compressor and includes a feather / spring plate. When cooling is needed the solenoid coil is energized, building up a magnetic field attracting the spring plate, which thereby is connected with the pulley. In this condition the compressor shaft is driven. The refrigerant therefore is circulated and cooling is achieved. To switch off the compressor the solenoid is de energized, the magnetic field disappears and the feather/spring plate is separated by return springs from the pulley, which then again runs freely without taking along of the drive shaft. For safety reasons a thermal fuse is located in the compressor clutch coil circuit. If belt slip occurs for example due to a blocked compressor heat is generated. If the heat reaches a certain value (around 180 °C) the thermal fuse is blown. This interrupts the power supply to the solenoid and the pulley can turn freely so that the clutch bearing and the pulley and belt will not be damaged. Once the fuse is blown the solenoid has to be replaced. Any clutch slipping should be traced to either incorrect clearance or low voltage to the clutch. Too small clearance can cause a scrapping of the plates; to big clearance will cause a weakened magnetic field. If these are checked and found correct and the clutch is still inoperative, it should be replaced. The approximate current consumption of the magnetic clutch is around 3 amps at 12 volts. Check the clutch coil resistance (3.0 – 3.2 Ohm) to determine the thermal fuse condition, and replace the clutch coil if required.

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Hose structure

As mentioned earlier the hoses for R134 a have to be different due to the smaller size of molecules. But still the hoses are the part where even under normal conditions refrigerant disappears and moisture enters the system.

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Condenser

The condenser consists of pipes and lamellas, which are firmly connected with the pipes to create a large heat exchange surface to reach a good heat transfer. The condenser is installed in front of the radiator. It cools high pressure and high temperature refrigerant to its condensation point and returns it to its liquid state. The hot gas enters the condenser with a temperature of 60°C to 100°C, but even if it is cooled down only by 2°C –3° C, it changes from gas to liquid because of the properties of the refrigerant. The heat exchange in the condenser takes place via air cooling. It is essential that the condensers are cooled efficiently by the passage of air through its fins. Any obstruction such as dirt, leaves, mud or any foreign matter, will reduce the lowering of refrigerant temperature, resulting in increased heat and pressure. In normal condition the condenser is at lower temperature than the car radiator but if the condenser efficiency is reduced its temperature increases. It may even become higher than that of the car radiator causing the engine to overheat. No routine maintenance is necessary for the condenser, apart from the removal of obstructions, and repairs can only be carried out if the condenser is removed from the car.

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Dryer

The purpose of the dryer is to temporarily store the liquefied refrigerant. It also has to remove dirt and moisture from the refrigerant. By different operating conditions, like thermal load at evaporators and condensers, number of revolutions of the compressor, a different amount of refrigerant is pumped through the system. For the reconciliation of these fluctuations a dryer is inserted. The liquid coming from the condenser is collected and stored in it, so that only the required quantity flows to the evaporator for the cooling of air. Additionally the dryer is able to bind a small quantity of water from the cycle, usually it can take 6 to 12 g water, and the quantity depends on the temperature. The quantity rises with lower temperature. Desiccant: for R 12 systems silica gel has been used as a desiccant to eliminate moisture, but in R134a systems in zeolite is used as a desiccant.

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Expansion valve

Basically we distinguish two types of refrigerant systems. TXV – Type: Thermal Expansion Valve Type CCOT Type: Clutch Cycling Orifice Type. Due to the fact, that there are some differences in components and working principle, the chart contains the differences among them.

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CCOT refrigerant cycle and components

* 1 kPa = 0.145 psi

Different to the expansion valve regulation the injection of liquid refrigerant takes place into the evaporator via a fixed throttle. This fixed orifice is located in the liquid line near the evaporator and has filter screens located on the inlet and outlet tube of the body. At the fixed orifice tube the liquid refrigerant begins to vaporize, because it only allows a proper amount of refrigerant to enter the evaporator, to get a good cooling effect. The state of the refrigerant immediately after the fixed orifice tube is 100% liquid. As soon as the liquid pressure drops, it starts to boil and by doing this it absorbs heat. This heat is removed from the air passing over the cooling fins of the evaporator which thereby is cooled. A pressure switch is used to control the amount of refrigerant entering the evaporator. When the S/W contacts are open and the clutch coil is not energized, the A/C clutch is disengaged and the compressor does not work. When the S/W contacts are closed the compressor magnet clutch coil is energized and the A/C clutch is engaged to drive the compressor. No adjustment or services can be made to the fixed orifice tube assembly which can't be removed from the line. The fixed orifice tube should be replaced whenever a compressor is replaced. * CCOT: Clutch Cycling Orifice Type

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Accumulator (CCOT): the Accumulator is located in the low pressure side of the refrigerant circuit. The inlet of the accumulator is connected to the evaporator core outlet tube by means of suction line. The refrigerant enters the accumulator canister through the inlet tube. The oil is separated at the bottom of the canister. The refrigerant passes the desiccant, where water and moisture are separated and is stored below the plastic cap. From there it is sucked through a U-pipe by means of the compressor. A small diameter oil return hole is located near the bottom of the canister. This allows Oil to enter the suction line at a controlled rate. To prevent dirt and moisture from entering the oil return hole, a strainer is fitted. * CCOT: Clutch Cycling Orifice Type

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Expansion valve inner equalizing type

The car interior will not be cooled sufficiently if the expansion valve outlet is too small. If it is too wide, frost will be produced on the evaporator, decreasing cooling efficiency. Thus the size of this small spray hole has to be controlled according to various conditions. The expansion valve also serves as a regulator of this spray hole. Depending on the overheating of the refrigerant gas at the evaporator exit, the TXV adjusts the amount of refrigerant entering the evaporator (depending upon the respective operation conditions), so that the heat exchanger surface of the evaporator is optimally used. The TXV is installed between high and low pressure circuit in the refrigerant cycle and before the evaporator. If the temperature of the refrigerant (which leaves the evaporator) rises, the refrigerant in the thermostat of the expansion valve expands and increases the flow of the refrigerant to the evaporator. If the temperature of the refrigerant decreases, it’s volume in the thermostat decreases and the flow to the evaporator is reduced. As seen earlier expansion valves can be classified into two types: External Equalizing Type, Inner Equalizing Type. The thermal expansion valve is regulated by the interaction of three forces: 1. The pressure in the sensor line, which depends on the temperature of the overheated refrigerant,

affects the opening strength of the diaphragm (PF). 2. The evaporator pressure affects the diaphragm (PE) in opposite direction. 3. The pressure of the adjustment spring (PS); it acts in same direction as the evaporation

pressure.

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Expansion valve external equalizing type

The external equalizing type consists of a thermal capillary tube charged with vapor refrigerant, a diaphragm power element, balancing spring, external equalizing pressure tube, valve seat actuating pin, metering valve, inlet port and screen and outlet port. The difference between the inner equalizing is that the external equalizing type has not only the heat sensing bulb, but also an additional pipe which is connected to the evaporator outlet. By this pipe the pressure can be detected at the outlet, very close to the place where the outlet temperature is detected. This allows a more accurate control, especially in the case that the evaporator has a high internal resistance. The upper diaphragm chamber reflects the evaporator outlet temperature and provides the differential action by opposing outlet temperature against outlet pressure. The outlet temperature acts on the heat sensing tube, which changes the pressure on top of diaphragm accordingly. This pressure tries to open the refrigerant inlet more to increase the amount of refrigerant passing the valve .Together with the spring force the outlet pressure acts underneath the diaphragm trying to close the inlet. The balance of these forces causes the inlet to be opened the correct amount, so that the required amount of refrigerant can enter the evaporator.

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Evaporator

A metered supply of low pressure, cold refrigerant is drawn through the evaporator by the suction side of the compressor. Heat laden air from the car exterior is pulled over the coils by a fan, and temperature difference between hot air and cold refrigerant cause’s heat transfer from warm air to cold liquid. As the liquid is absorbing heat from the air, the refrigerant is caused to vaporize. When the refrigerant is just vaporized completely the so called saturated condition is reached, but the vapor has more coils to pass through before its exit, so that it absorbs more heat. This condition is called superheat. Condensation of the moisture in the air occurs simultaneously with the reduction of air temperature. This water condensate is drained out of the evaporator assembly and discharged through drain pipes. Frequently condensate will drain from the evaporator case very soon after the car comes to rest and the blower is switched off creating a puddle underneath the car. This is a natural condition and no investigation as to the cause is necessary. No routine maintenance is required to the evaporator, but may be some cleaning is required from time to time due to bad smell.

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Refrigerant flow control

When the vapor pressure of the operating system is stable, Pf =Ps condition will prevail. The needle valve opening at this time will be stationary (at a preset condition) and a constant refrigerant flow will be maintained. PF / PE = PS / PE Constant refrigerant flow: If the amount of refrigerant in the evaporator becomes less, the refrigerant will vaporize faster. Thus, the temperature in the equalizer circuit rises, causing the gas in the upper diaphragm chamber to expand and the valve will be opened. This results in a larger flow of refrigerant into the evaporator. PF / PE < Ps Flow of refrigerant will increase. Conversely, if the amount of refrigerant in the evaporator becomes greater, the refrigerant will vaporize slower. The temperature in the equalizer circuit drops, causing the valve to close. This results in a lower flow of refrigerant through the circuit. PS > PF / PE Flow of refrigerant will decrease.

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Ac operation cycle

If the refrigerant cycle is actuated, i.e. the air conditioning system is switched on; the compressor draws out cold, gaseous refrigerant from the evaporator, compresses it and delivers it to the condenser. The compression will heat up the gas. The compressed, hot gas is cooled down in the condenser by outside air or an auxiliary blower. When reaching the dew point (depends on the pressure, see boiling point table) the refrigerant condenses and becomes liquid. The completely liquefied refrigerant coming from the condenser is collected in the tank incorporated in the dryer. The function of this arrangement is to ensure that only clean moisture free liquid is transferred to the evaporator. Next the refrigerant flows to the expansion valve. The high pressurized liquid refrigerant is injected into the evaporator whereby the pressure is lowered so that the refrigerant evaporates. The heat necessary for vaporization is extracted from the outside air passing the evaporator lamellas, so that the air is cooled down .The completely gaseous refrigerant leaving the evaporator is drawn in by the compressor and is compressed again. The refrigerant cycle is closed.

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Heater unit

When engine coolant flows through the heater core, heat from the coolant is transferred to the cooler air flowing through the fins of the heater core. By the combination of cooling and heating system the temperature can be adjusted to the desired, comfortable level.

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Electric circuit

* This schematic diagram is only available in MG Optima/ Magentis model.

et’s have a look at the wiring diagram to determine which electrical parts are involved in the air L

conditioning: for example the ambient temperature sensor, the AQS sensor, the AC relay etc. Now let’s look at them individually.

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Dual pressure switch

The dual pressure switch is safety devices which will switch OFF the compressor by turning OFF the Electro Magnetic Clutch (EMC) when abnormal conditions (pressure too low or to high) are detected. The following types of pressure switches are used in KIA vehicles: Dual Pressure Switch, Triple pressure switch, APT sensor. The pressure switch can be installed either in the refrigerant line between condenser and dryer or in the dryer itself. Let’s start with the simplest one: the dual pressure switch. The dual pressure switch is used to switch on and off the compressor. Under normal conditions power is supplied to the EMC via the pressure switch. To protect the compressor from getting seized under low pressure conditions the switch will open and the power supply to the EMC is cut. To prevent pressure being raised to high and thereby protecting the parts from bursting the switch will also be opened and the power supply to the EMC is cut.

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Triple pressure switch

The triple pressure switch is a combination of the low pressure switch (for checking the quantity of refrigerant) and the high pressure switch (for prevention of air conditioning line burst) and a medium pressure switch (for cooling fan operation). When the pressure drops to approximately 2.3 bar or lower the compressor is stopped, thus preventing the compressor from being damaged by sticking. When the pressure rises to 32 bars or higher the compressor is also stopped to prevent air conditioning lines from bursting. When the pressure reaches 15.5 bars or more, the condenser fan runs at high speed to cool down the refrigerant to stabilize its pressure.

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APT sensor

The APT (Automotive Pressure Transducer) is a capacitive based sensor. It senses the pressure of the refrigerant by a linear voltage output directly proportional to applied pressure. The pressure will deform a diaphragm which is one part of the capacitor. The other part is the ceramic substrate. As the electric field strength of a capacitor depends also on the size of the dielectric, the field strength varies according to deformation of the diaphragm. The ASIC converts this change into a output voltage accordingly, which is then send to the FATC controller. There is 0.2V (not 0V), if the refrigerant line pressure has gone to 0, for communication to engine ECM (0V means poor contact or open circuit). There is 4.8V; even if the line pressure is over the standard value (high pressure) (5V means short circuit). The APT is usually combined with a multi speed fan for step less control of cooling fan speed.

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Multi speed fan with PWM control

Besides using the APT signal for the circuit protection and fan control, there are some other changes to the system, which can be seen in the system diagram. A so called multi speed fan is used, which allows a step less control of the fan speed. The speed of the fan is controlled by a PWM (pulse width modulation) module.

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Cooling fan control

The cooling fan speed is controlled by the PWM control module according to the signals from the ECM or PCM. 10 percent duty means fan is off, 90 percent means full speed operation. The control is step less from zero to full speed. The control is made according several parameters. These are: engine coolant temperature, A/C switch, APT sensor, Vehicle speed. The actual fan speed is depending on the operating conditions and the correct function can be determined by the usage of the chart.

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Thermostatic switch

On both systems (TXV and CCOT) you find a Thermostatic Switch. The function of the thermostatic switch is to prevent the evaporator from icing. If the temperature at the evaporator fins is less than 0.5°C, the compressor is switched off.

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Fin sensor / thermistor

Either thermistor or fin sensor are installed to prevent the evaporator from freezing. Electrically the thermistor is installed in the line to the compressor clutch. It opens and closes according to the evaporator temperature, thereby switching off and on the compressor. Compressor off is made at approximately 0,5 degree and back on at approximately 3 degree. For exact values, please refer to the individual workshop manual. The Fin sensor is not switching on and off, but changing its resistance according to the evaporator temperature. This change of resistance is used by the control unit to decide the compressor is switched on and off. For information of the resistance according to the temperature, please refer to the manual.

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Blower motor speed control

According to the position of the blower switch different terminals are supplied with power. As their effective resistance differs, also the output voltage and thus the blower speed vary. Note: Blower speed control for FATC is covered in FATC section.

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Maintenance and trouble shooting

Please note that the air-conditioning system can loose up to 15 percent refrigerant per year and that the average border of operation is around 60 percent filling grade. Maintenance of the air-conditioning can also decrease fuel consumption! As it influences for example the operation time of the compressor. Note that a broken compressor may require a change of receiver / drier due to contamination with metal parts etc and that a broken condenser etc may require the change of the receiver /drier due to much moisture!!!

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Pollen filter

The purpose of the air-filter element is to remove dust and odor. Filter replacement period is 5.000 – 12.000 km, depending on the environmental conditions. Please note that a clogged filter will influence cooling and heating efficiency and can be a cause for allergy. For filter replacement: Remove the glove box. Remove the locking part of the air filter cover.

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Safety precautions

Refrigerant can make a person very sick when inhaled, even if inhaled only a little at a time over a period of time it may be cumulated resulting in a toxic condition. Should liquid refrigerant strike you anywhere else on the body, follow the procedures as outlined. Splash on cool water to raise the temperature and apply clean petroleum jelly. If liquid refrigerant strikes the eye, the eyeball may be frozen which can cause blindness. If liquid refrigerant should strike the eye, do not rub it. Follow these instructions: Splash large quantities of cool water into the eye to raise the temperature. Apply clean petroleum jelly to the eye to avoid infection. Cover it with an eye patch to avoid the possibility of dirt entering the eye. Visit a doctor or hospital for immediate professional aid. Do not attempt to treat it yourself.

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Never heat a refrigerant cylinder above 52°C as it may burst. Use an approved valve wrench for opening and closing valves to avoid damage. Secure all cylinders in an upright position for storage and withdrawal of refrigerant. For full information about safety advices refer to the workshop manual.

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Preliminary checks

* Refer to W/shop manual for more details.

Preliminary check including visual inspection of the system. Check condenser fins for blockage or damage. Make sure that the drive belt is installed correctly and check its tension. If the proper tension is not maintained, belt slippage will greatly reduce air conditioning performance and drive belt life. Check / adjust the air conditioning drive belt at the time of new-car preparation. Check drive belt tension at regular service intervals and adjust as needed. Next start the engine, turn ON the A/C Switch, and check that the A/C operates at each position of the blower switch except 0 positions. Check the magnetic clutch operation. Check whether the idle RPM increases when the magnetic clutch is engaged. Check for the correct condenser fan operation. NOTE: Conditions can vary depending on the model. Please refer to the Workshop Manual.

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Bad smell

* All the device and tools in this slide is not for officially suggested one by KMC but for the training purpose.

Sometimes customers complain about a “bad smell” when they switch on the Air condition. The reasons are bacteria, which build up on the evaporator coils. If the Air condition is not used regularly, these bacteria build up much quicker. The presence of theses bacteria in the air can cause allergic reactions. If a customer complains about a “bad smell” of an Air condition, it is recommended to clean the Evaporator by using an Air conditioning system cleaner.

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Leak detector and leak test

* All the device and tools in this slide is not for officially suggested one by KMC but for the training purpose.

The leak detector is used to detect leaks in air conditioning systems. It features a sensitivity selection switch which allows it to be used for CFC and HFC air conditioning systems. It can detect leaks as small as approx. 14.15 grams per year. ON/OFF and BALANCE: The same control turns on the unit and enables you to control the sensitivity for eliminating background contamination to find leaks easily. VISUAL LEAK INDICATOR: the 10 LED light up to show increasing levels of concentration, one LED indicates a minimal amount of refrigerant is reaching the sensor while all 10 indicate big leak or concentration. LOW BATTERY INDICATOR: if only the top LED is lit, the batteries should be replaced. AUDIABLE LEAK INDICATOR: The normal operating sound is a steady ticking as you move the probe closer to the leak, the tone will change to a faster ticking sound and then to an alarm sound. VOLUME: allows you to adjust the audible leak signal. SENSITIVE LEVEL: can be used for a wide range of refrigerant, the correct sensitivity level should be selected. Use these examples as a guideline: Level 1 CFC + HCFC such as R-12 R-22 R-500 R-502 Level 2 HFC as R-134a HP 62 AC9000 AZ 20 AZ 50 NOTE: A gas leak tester purely designed for R-12 systems can not be used for detecting leaks of the R-134a gas because of insufficient sensitivity. The newly introduced leak tester has a higher sensitivity and can be used for both the R-12 and R-134a refrigerant.

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1. Turn the ON/OFF switch to ON 2. Select the sensitivity level by sliding the switch to the “1” setting or “2” setting. 3. Adjust the Balance: turn the BALANCE control until a loud alarm sound can be heard, then turn

it down until you hear a slow, steady ticking 4. Begin searching for the leak. The recommended scan rate is 2 to 5 cm per second with the

sensing tip as close as possible to the area being searched but not touching it. 5. To pinpoint a leak, you may need to adjust the balance. When you are near of a concentration of

refrigerant, the alarm tone will sound. Keep the probe in the same position and turn the balance control down until you hear the ticking sound again. Then continue searching for the leak. You may have to re-balance the unit several times if there is a large leak and refrigerant has accumulated.

6. If you find more than one leak, or if you suspect more than one, repair the larger leak first so that pinpointing the smaller leak is easier. Follow the described steps to perform a leak test on a completely empty system: Attach an air conditioning service station and charge the system to about 100kPa. (Please note that this is not allowed in all countries, refer to the local regulations!) Check the system for leaks using a leak detector. If you find leaks that require the system to be opened (to repair or replace hoses, fittings, etc.) remove any charge in the system according to the discharge procedure. If a gas leak is detected, proceed as follows: Check the torque on the connection fitting and if necessary, tighten to the proper torque and check again. If leakage continues even after the fitting has been retighten, discharge the refrigerant from the system, disconnect the fitting, and check the seat for damage. Replace fitting, even if the damage is slight. After checking and repairing leaks, the system must be evacuated to remove moisture.

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Leak test with fluorescent

* All the device and tools in this slide is not for officially suggested one by KMC but for the training purpose.

Another method of leak detection is to add a special additive to the refrigerant, which can be detected by using a special lamp. For maximum visibility, test for fluorescence in a darkened area. Fluorescing may bright or dim, depending on the amount of fluorescing agent present. Be careful to distinguish fluorescence from blue light reflection on polished metal surface. Please note that after leak detection and repair area should be cleaned to avoid that next time the old liquid may mistaken for a leak. Fluid injector: its purpose is to inject Oil / Leak Fluid to the system.

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Basic gauge set

Once you have attached the gauge set to the system, you are in a position to accurately diagnose an internal system problem, without relying on guess work. Your gauges are the most important diagnostic tool and knowing what they are telling you is the key to accurate and fast system troubleshooting. The test gauge indicators shown on the following pages are to be used as typical examples of common problems which you may need to diagnose. Varying equipment and conditions may cause your actual gauge readings to be different from those shown in this section. The gauge manifold set is the most important tool used to service air conditioning systems. The manifold test set is used to determine the systems high and low side gauge pressures, the correct refrigerant charge and operating efficiency. It is designed to read both the high and low sides at the same time, because this pressure must be compared with each other to determine the correct system operation. Due to various makes and models of equipment available it would be impractical to describe the operation of each, so we will concentrate on the basic gauge set and readings which are universal. Before attempting to use any gas charging or test equipment you should be thoroughly familiar with the manufacturer's operating instructions. Refer to the workshop manual and the owner’s manual of the gauges.

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Low Side Gauge: this gauge has a dial reading from 0 to 24 bars in clockwise direction and from 0 to –1 bar (vacuum scale) in counterclockwise direction. Also you can see a temperature scale, reading from –30 to +35°C. This low side gauge is called a “Compound Gauge” and has the purpose to indicate both, pressure and vacuum. This gauge is used to measure the evaporator outlet pressure. High Side Gauge: this gauge has a dial reading from 0 to 34 bars in a clockwise direction. Also you can see a temperature scale, reading from 0 to +88°C. The high side gauge is a pressure gauge only. We refer to all pressures above atmospheric pressure as gauge pressures, and all pressures below atmospheric pressure as a vacuum. Zero gauge pressure will remain zero regardless of what the altitude is.

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Air conditioning

Performance check

Performance Test Connect the gauges, open all doors, set the cooling to max cool and the blower to highest speed and run the vehicle with 2000 rpm. The gauge readings are the prime indicator about the system operating conditions, but as the system efficiency is influenced by the ambient temperature and the relative humidity these values have to be measured also. Place a thermometer in the cool air outlet and measure the temperature of the cooled air. Use a psychrometer (dry and wet) to determine the relative humidity (or use a device which indicates humidity directly). Measure the ambient temperature close to the condenser and calculate the difference between the inlet and outlet temperatures. Check that the intersection of the relative humidity and temperature difference is within the darkened area. If this is the case the cooling performance is sufficient. To stabilize the system: operate the system under these conditions for 5-10 minutes and the system will be stabilized and ready for test readings.

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Discharging and adding of refrigerant

If a very low refrigerant charge is indicated by the preliminary test data, a partial refrigerant charge will have to be added to bring the system charge up to a point where accurate, meaningful tests can be conducted. This adding of a partial refrigerant charge can be performed during the time the system is being stabilized. The procedure for adding a partial charge is explained later in the text. Note that some refrigerant loss will possibly occur over a year and that this is recognized as normal. Vibration, hose porosity, and the general construction of the system make a leak proof system nearly impossible. Replacing this partial charge of refrigerant will constitute much of the quick service type of air conditioning work with which you will come in contact. Adding Refrigerant: if the container with refrigerant is not already connected to the manifold gauge set centre hose connect it now. Loosen centre hose connection at gauge manifold, open can valve for several seconds to purge air from the centre hose, then tighten hose connection and close can valve. Start the engine and operate air conditioner. With system operating, slowly open the low side manifold hand valve to allow refrigerant to enter system. The low side of the system is the suction side and the compressor will pull refrigerant from the can into the system. With refrigerant container in upright vapor position, add refrigerant until gauge readings are normal. But never turn a can to a position where liquid refrigerant will flow into the low side of the system. Close low side manifold hand valve and refrigerant can valve. Continue to operate the system and check for normal refrigerant charge. Do not overfill. Please note that nowadays the charging is made with a special recycling device, which allows emptying the system completely and recovering the refrigerant it is possible to fill the system accurately with the specified amount.

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System evaluation by pressure gauges: Normal condition

If the system is in good condition, the low pressure side is between 1.5 – 2.5 bars and the high pressure side is 8-22.5 bars. Nowadays the gauge set is normally built into the service station, but the use of them remains the same as with separated ones.

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Low refrigerant charge

Symptom: Insufficient cooling Diagnosis: Insufficient refrigerant amount / leakage. Keep in mint: a certain amount per year may leave through hoses etc. Leak check required! Possible cause: Gas leakage of AC system. Correction: If compressor operation stopped due to low pressure refill refrigerant, then make thorough leak test. Discharge refrigerant from the system if necessary to replace units or lines. Do not forget to check the compressor oil level. System may have lost oil due to leakage of refrigerant.

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Moisture in the system

Symptom: Sometimes cooling is o.k. sometimes insufficient (alternating) Diagnosis: Moisture in the system Possible cause: Drier in oversaturated state Correction: Replace drier and remove moisture in system through evacuating.

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Air in the system

Symptom: Insufficient cooling Diagnosis: Pressure to high on both high and low side, Low side piping warm to hot .Pressure on high side is more than 1 bar higher than it should be compared to saturation pressure which corresponds to outlet temperature of the condenser. Possible cause: Air in the system Correction: Empty the system, evacuate the system, check for leaks and refill.

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Clogging of the drier

Symptom: Insufficient cooling Diagnosis: Both pressures are low and the difference between drier inlet / outlet temperature is higher than 5 °C. Maybe pipe after drier is frosted. Possible cause: Drier clogged Correction: Replace drier.

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Expansion valve stuck close

Symptom: Discharge Air – Slightly cool, Expansion valve – Sweating or frost build up Diagnosis: Expansion valve stuck closed, Screen plugged, Sensing Bulb Malfunction Correction and testing: If expansion valve inlet is cool to touch, proceed as follows: Set air conditioner for maximum cooling and operate the system. Spray liquid refrigerant on head of valve or capillary tube. Note low side gauge reading. Low side gauge should drop into vacuum. NOTE: This test may not be possible on some vehicles if expansion valve or capillary tube is not accessible! If low side vacuum reading was obtained, warm expansion valve diaphragm chamber with hand, then repeat test step (b) Outer equalizing type: If expansion valve test indicates valve operation is satisfactory, clean contact surface of evaporator outlet pipe and temperature sensing bulb. If expansion valve inlet shows sweating or frost, proceed as follows: Discharge system, disconnect inlet line at expansion valve and remove and inspect screen, clean and replace screen and reconnect inlet line. Proceed with correction procedure. If expansion valve test indicates the valve is defective, proceed as follows: Discharge system, replace expansion valve, and then proceed with correction procedure

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Expansion valve stuck open

Symptoms: Insufficient cooling, Evaporator – Sweating or frost Diagnosis: Expansion valve stuck open, check for expansion valve stuck open or incorrect mounting of temperature sensing bulb as follows: set air conditioner for maximum cooling and operate the system. Spray liquid refrigerant on head of valve or capillary tube. Note low side gauge reading. Low side gauge should drop into vacuum. If low side vacuum reading was obtained, warm expansion valve diaphragm chamber with hand, then repeat test step. Outer equalizing type: if expansion valve test indicates valve operation is satisfactory, clean contact surface of evaporator outlet pipe and temperature sensing bulb. Correction: if expansion valve test indicates valve is defective, proceed as follows: Discharge system, replace expansion valve, making sure all contacts are clean and secure. Then evacuate system and recharge system it, then check performance.

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Condenser malfunction or overcharge

Symptom: insufficient cooling, High Side Lines – Very hot Diagnosis Condenser air passages clogged or fan problem If the compressor suction pipe is frosted the system may be overcharged Correction: check for loose or worn fan belt which could be adversely affecting condenser air flow. Check cooling fan (Viscous and electric type) Inspect condenser for clogged air passages or other obstructions preventing air flow through the condenser. Inspect condenser mounting for proper radiator clearance. Inspect cooling fan for proper operation. Inspect radiator pressure cap for correct type and proper operation. After making above corrections operate system and check performance. IF CONDITION IS NOT CORRECTED: With recover system : just recover the refrigerant to see the amount, otherwise inspect system for overcharge of refrigerant and correct as follows: discharge refrigerant until both, high and low side gauge readings drop below normal. Add refrigerant until pressures are normal, than add 50g – 100g refrigerant additional. Operate the system and check performance. IF GAUGE READINGS STILL TOO HIGH Discharge system, remove and inspect condenser to ensure free passage of refrigerant or replace condenser. Replace receiver – drier, evacuate the system Charge system and check performance.

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Compressor malfunction

Symptom: Insufficient cooling Diagnosis: Pressure to high on low side and to low at high side. Frost on low pressure piping possible, Compressor may be noisy, maybe internal valve broken Correction: Repair /Replace compressor. NOTE: If compressor is not noisy with these conditions, problem may be loose or worn compressor

drive belt.

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Special service tools

Here are some of the required special tools as a sample that professional service needs special tools.

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Disassembly of clutch and pulley

The disassembly of the clutch and pulley is a sample of a procedure with the use of special tools. Always refer to the shop manual for the correct procedures and tools.

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Air gap measurement

Depending on the compressor and clutch type, you may use a feeler gauge to determine the clutch air gap or a dial gauge (if you can't insert a feeler gauge).If it is not possible to insert a feeler gauge, (for example on compressor HS-11) perform the following steps: Take a dial gauge and place it on the “outer ring” of the compressor clutch. Set dial gauge to zero. Apply voltage to the coil and check the reading of the dial gauge. The reading should be within the specifications (refer to Workshop Manual). NOTE: When reassembling the compressor assembly, clean the pulley bearing surface and coil

press diameter of the front head to remove any dirt or corrosion. Reassembly: after reassembling the compressor assembly by the reverse of the disassembly procedure given, check the clutch air gap between the clutch hub and the pulley mating (refer to Workshop Manual).

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Pressure relief valve

The Pressure Relief Valve of R12 is a melt bolt type and part of the drier. In case of overpressure all refrigerant is released into the atmosphere. The pressure relief valve R134a is a pressure control spring type; it releases only the amount of refrigerant into the air which is too much. NOTE: If you do not eliminate the cause when the pressure relief valve is triggered, it may be

triggered again. If the pressure relief valve has been triggered by abnormally high pressure, do not use it again! In normal operation, the high pressure switch is triggered first and the compressor stop, so the pressure relief valve is not triggered so easily.

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Oil specifications

Compressor – Oil: the oil used with R12 Air Conditions is for lubricating the mobile parts. It’s a high-distilled mineral oil which is free from impurities such as sulfur, wax and humidity. Wrong oil can result in copper plating and formation of arrears. Premature wear and destruction of the mobile parts of the system would be the result. R134a Air conditioning systems use special synthetic refrigerator oils, e.g. Polyalkylenglykol (PAG). These oils can not be used in R 12 air conditions, since they don't have a mixing proportion with this refrigerant. Circulated refrigerator oil constantly mixes (approx. 20 to 40 % depending upon the type of compressor and refrigerant quantity) with the refrigerant in the cycle, and lubricates the mobile parts. Types of oil for R 12: Mineral oil Types of oil for R 134a: PAG, Ester. In order to prevent wrong compressor oil charging, the types of suitable refrigerant and compressor oil are clearly specified in the part of the compressor for R134a. PAG-46 will be replaced by PAG-100 with a higher viscosity. NOTE: Do not store refrigerator oil open (hygroscopic) always keep oil reservoirs closed. Do not

use old (used) refrigerator oil.

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OIL level adjustment

There is no way to check the oil level while the compressor is installed, but the level should not change throughout normal service. Too less oil results in a insufficient lubrication of the compressor which can result in seizing of the compressor. Too much oil leads to an unsatisfactory cooling performance of the air conditioning system (insufficient heat transfer). The pressure of the compressor excessively rises, which can lead to damage. The required amount of compressor oil for lubrication is charged into the air condition cycle where it dissolves in the refrigerant to circulate throughout the cycle. As a result the oil will remain in each component of the cycle when the air- conditioning is turned off. During replacement of major parts, if an amount of oil equal to the amount remaining in that part is not supplied to the cycle, the amount of oil will be insufficient, leading to inadequate lubrication. Therefore, add new compressor oil in the amounts indicated in the workshop manual.

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Hose and pipe connection

Handling Tubing and Fittings The internal parts of the refrigerant system will remain in a state of chemical stability as long as pure moisture free refrigerant and refrigerant oil is circulating. Abnormal amounts of dirt, moisture or air can upset the chemical stability and cause troubles or even serious damage. The following precaution must be observed: When it is necessary to open the refrigerant system, have everything you will need to service the system ready on hand. Do not leave the system open longer than necessary, as moisture will enter the system. Cap or plug all lines and fittings as soon as they are opened to prevent the entrance of dirt and moisture. All lines and components in stock should be capped or sealed. Never attempt to rebind formed lines to fit. Use the correct line for the installation you are servicing. Keep all tools clean and dry. Replace o-rings and fittings with new ones. Observe the specified tighten torque at each fitting. Release spring lock connectors: they are spring-loaded in the closed position. They were used in early models; they are not used anymore due to some leakage problems. Refrigerant oil will damage the paint! Do not spill it onto the vehicle, if this happened accidentally, wipe it off immediately.

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FATC system: AC control

When the ignition is in ON position, battery voltage is applied to the coil on the control side of the A/C relay. With the A/C switch ON, voltage from the FATC Control Module passes through the normally closed contacts of the triple switch, thus entering the ECM. When the ECM receives the A/C ON signal, it will apply a ground to the control side of the A/C relay, allowing the relay contacts to close. Now battery voltage passes through the relays contacts to energize the EMC and the compressor is operated.

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AC control signals

The electronic control detects the temperature level selected by the vehicle occupants and the operating conditions of the system (via the sensors). Using this information the control unit not only controls the compressor operation, but also activates the different actuators for air distribution – depending upon the program which the vehicle occupants have selected. Besides using automatic mode all of these control circuits can be manually influenced.

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Component location

On this sample scheme you can see the approximate location of the air condition components. For specific vehicles, refer to the related shop manual.

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HVAC unit

It can be recognized that in modern vehicles the different components of the heating and the air-conditioning system are combined to a functional unit the so called HVAC unit, which nowadays contains the heater core, the evaporator and the blower fan as well as actuators and sensors. The picture also indicates the location of sensors and actuators installed to the HVAC unit (sample).

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Controller FATC without AQS

Scheme of the Control panel without Air quality system.

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Temperature unit change

Here is a sample how the temperature indication can be switched between C° and F°. For individual cars please see WM

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Controller FATC with AQS

Scheme of the Control panel with Air quality system.

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Controller FATC with dual mode

Dual mode button: Pushing the dual mode button (green LED ON), allows the driver and occupant to set the temperature individually. The actuators are located on the left (driver actuator) and right (passenger actuator) side of the heater unit. Note: Air discharge mode can't be controlled individually! Temperature Setting C° to F°: The user can change the temperature indication between C° and F° by pushing the dual button for 3seconds, while pressing the mode button. Note: Temperature will be indicated in C° if battery was disconnected!

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Switch functions

The use of the individual switches is shown above.

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Control logic and CELO function

In-car temperature correction: when the in-car sensor detects a sudden steep temperature change, controller corrects the temperature differences slowly. (1°C up / 4sec delay / 1°C down / 4sec delay) Ambient temperature correction: when the ambient sensor detects a sudden steep temperature change, controller corrects the temperature differences slowly. (1°C up / 3 min delay (ex. Underground, tunnel) / 1°C down / 4sec delay) Heat radiation correction: when the photo sensor detects a sudden steep solar radiation change, controller compensates it slowly. (350 → 1000 (W/m2) / 1 min delay 350 ← 1000 (W/m2) / 5 min delay) Temp. Door control: temperature door angle is automatically controlled according to the selected temperature and other sensor signals. Blower speed control: AUTO mode (linear control) / MANUAL mode (7 step control) Mode control: AUTO: Mode changes automatically according to the selected temperature and other sensor signals, manual: Mode changes when the mode switch is selected Intake door mode: the FRE/REC door state can be changed at AUTO mode according to the input data combination. Compressor on/off control (AUTO mode) Fin sensor: lower 0.5°C → Compressor OFF over 3°C → Compressor ON Max. Hot function (When 32°C is selected at AUTO mode) Temp door: MAX HOT side, Mode door: Floor mode, Intake door: FRE mod, Compressor: OFF, Blower speed: MAX high CELO (Cold Engine Lock Out) function

Ambient temperature＜10 ℃, Water temperature: below 73 ℃, Air direction mode: Auto or Floor,

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Blower speed: Auto

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In-car Temperature sensor

In-car Sensor The in-car sensor is located on the lower crash pad as shown in the picture. It contains a thermistor, which measures the temperature of the air inside the passenger compartment. It senses the passenger compartment temperature, changes the resistance value, and enters the corresponding voltage into the automatic temperature control module (FATC).

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Photo sensor

The photo sensor is located close to the driver side defrost air duct. In response to photo intensity level in the vehicle, the sensor will send corresponding signal to the control module to control the blower level and discharge temperature. It contains a photovoltaic (sensitive to sunlight) diode. Inspection: Emit intensive light toward driver side and passenger side using a lamp, and check the voltage change between terminals 1 & 2.

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Air quality sensor (AQS)

Many drivers select the recirculation or fresh air mode manually to intercept the inflow of harmful exhaust gas, in spite of inconvenience and danger, while driving. AQS detects exhaust gas of neighboring vehicles and intercepts automatically. Although they detect the exhaust gas and manually close the inlet of the vehicles trapping the fumes inside, it is far too late to protect their health because they already inhaled the exhaust gas. Inversely, if driving with the inlet of the car closed completely, the shortage of air and the accumulation of carbon dioxide (CO2) will occur. This causes fatigue, headache, enervation, and drowsiness. AQS gives a perfect solution to these problems. The Air Quality System detects exhaust gas of neighboring vehicles and intercepts automatically. Manual operation is also available When the Air Quality System detects hazardous gas in the atmosphere less than the set value, High signal, i.e., 5V is generated. FATC Module controls Intake Actuator in the Fresh Mode based on this signal. If the Air Quality System detects hazardous gas in the atmosphere higher than set value, Low signal, i.e., 0V is generated. FATC Module controls Intake Actuator in Re-circulation Mode based on this signal.

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Water temperature sensor

The water temperature sensor is attached to the heater core inlet tube and detects the coolant temperature in the heater core. This signal is used for a precise control of the temperature and enable the controller to carry out Cold Engine Lock Out (CELO) function by comparing the differences among the water temperature, set temperature, inside temperature and outdoor temperature etc. Water temperature sensor check: Immerse the water temperature sensor in water and measure the resistance heating the water by comparing it to the specific values given by the workshop manual.

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Humidity sensor

The humidity sensor detects the relative humidity within the cabin. This sensor converts the humidity value into a voltage signal send to the FATC controller. If the in-car humidity and ambient temperature are exceeding a certain range, the FATC Control module turns on the compressor to prevent fogging.

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Humidity sensor specification

1). Sensor type: High polymer impedance variation sensor 2). Rated voltage: DC 5V. 3). Current consumption: below 10mA 4). Temperature range: 0 - 60°C 5). Humidity range: below 99% relative Humidity 6). Terminals: 3 terminals (DC 5V, Ground, Sensor output)

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Ambient temperature sensor

The ambient temperature sensor is located at the front of the condenser fan shroud. It detects the outside air temperature and converts it to a voltage signal which is send to the control unit.

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Blower motor speed control

The Blower speed on the FATC is controlled by the fan control switch and power transistor.

When the blower switch is at position 6, the high speed blower relay will be grounded by the controller. Therefore the fan is supplied with battery voltage and operates at highest speed.

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Power transistor inspection

In ranges other than 6 the speed is controlled by the controller via the power transistor. In order to measure the battery voltage after the blower motor the fan must be off. In range 1-5 the variable voltage should be detected for the base voltage (and of course also for the voltage after blower motor).

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MOSFET transistor

Recently the blower speed is controlled via an MOSFET transistor, which allows eliminating the high speed relay due to its properties. MOSFET (Metal Oxide Semiconductor Field Effect Transistors) have been used in power electronics applications since thee early 80's due to their appreciable current carrying and off-state voltage blocking capability with low on-state voltage drop. The MOSFET Transistor has three gates. D: Drain, G: Gate, S: Source Operating Principle of N-Channel Enhancement MOSFET The drain and source are negative doted areas, which are separated via a positive doted substrate (P). This substrate acts as a barrier for the electron flow; therefore no electrons can flow from the source to the drain in off condition (Blower off). When voltage is supplied to the gate a negative charged area (N) is created between the source and the drain, so that the electrons can flow (blower on). The strength of the current flow depends on the supplied voltage to the gate, as this weakens or enhances the field strength: in accordance the speed of the blower is increased or reduced.

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Intake door actuator

The intake door actuator (fresh/recirculation actuator) is located beside the blower motor assembly. The intake door actuator allows choosing between fresh (outside) air or re-circulated inside air by moving the intake (fresh/recirculation) door to the desired position. When the door has reached it’s desired position, the actuator stops. The position of the intake door can be selected manually by pressing the re-circulation switch or automatically by the air quality system (if equipped). Please note that in the case of automatic mode the intake door may re open after a certain time even the air is still contaminated (for example driving through a long tunnel). This is due to the fact that the sensor has adapted itself to the new environment conditions and uses this as a base for the judgment and also to avoid the lack of fresh air. If required the intake door can be closed by the manual operation in this case.

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Mode door actuator

The mode door actuator is located beside the heater unit. Inspection: Apply 12V to mode actuator terminal 7 and ground terminal 6. Verify that the mode actuator operates as below when grounding terminals 5, 4, 3, 2 and 1 in sequence.

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Temperature door actuators

The temperature door actuator is located on the bottom of the heater unit. The actuator controls the position of the temperature blend door based on the voltage signal from the FATC module. A potentiometer inside the actuator sends a feedback signal to the controller. When the required door position is reached, the controller cuts the voltage signal to stop the temperature door actuator.

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PTC heater

Some models equipped with diesel engine are equipped with an additional heater due to the fact that the heating of the cabin may be is insufficient due to the fact of the high efficiency of the engine. Due to this the waste heat is not sufficient to heat the cabin properly. To cope with this, additional heater systems are installed. There are some variants of additional heater systems: devices which are burning fuel in an additional device, special plugs in the water circuit or the PTC heater shown in the picture. PTC heater data: Current Min. 9.8A Max. 30A, Power 1000W, Resistance 0.4 Ohm

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PTC heater control

The three heater relays are located in a separate fuse box inside the engine compartment. If the input signal received by the ECM is within a specified threshold, the Heater Relay 1 is grounded by the ECM, thus closing the relay and supplying current to the heater circuit 1. The ground signal from the ECM is also supplied to the FATC or manual controller, thus informing the FATC/Manual controller to turn on the heater relays 2 and 3 after a specified period of time. The PTC heater operation condition is as follows (sample): Engine rpm over 700, ambient temperature below 15°C, battery voltage between 8.5V – 12.5V, engine coolant temperature below 70°C, and blower ON .The maximum operating time of the heater element is 60 min. The outside temperature signal for controlling the PTC heater is measured by the intake air temperature sensor inside of the mass air flow sensor. The PTC heater element is connected to the PTC heater relays by a 5-pin connector with the following arrangement: 1. 12V Heater relay 2, 2. Ground, 3. 12V Heater relay 1, 4. Ground, 5. 12V Heater relay 3

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If the PTC heater has to be switched on it follows the sequence shown in the picture to avoid a steep increase of power consumption. Furthermore the ECM and FATC / manual controller monitors the battery voltage every 15 seconds. If the battery voltage drops below 8.5V, the FATC/Manual Controller switches off Relay 3. If the battery voltage is still abnormal, the FATC/Manual Controller switches off the heater relay 2. n the cases that the battery voltage is to low the control logic changes as follows: PTC 1 + 2 + 3 (15 seconds)⇒ PTC 1 + 2 (15 seconds) ⇒ PTC 1

If the PTC relay 1 fails the complete heater circuit is inoperative and a DTC will be stored in the ECM (P1634 heater relay open / short

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FATC diagnosis

The FATC module self diagnosis test detects electrical malfunction and provides error codes for system components in this case. The method of activation can differ from car to car therefore consult the WM. In later models it is possible to read out the trouble code by the Hi-scan pro. The system can be also diagnosed with Hi-scan pro. The FATC module communicates with high-scan and diagnosis test feature will detect electrical malfunction and provide error codes for system components with suspected failures. It is not only possible to read out the trouble codes, but also to see the current data and to do actuator tests as in many other systems. If you do not have the Hi-scan pro available it is also possible to read out the trouble code by the internal fault detection.

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