-Technical Service Training Global Fundamentals Curriculum Training – TF1010011S Electrical...

Student Information

FCS-13197-REF CG7967/S 05/2001

Technical Service Training

Global FundamentalsCurriculum Training TF1010011S

Electrical Systems

Introduction Preface

Service Training 1

Global fundamentals training overview

The goal of the Global Fundamentals Training is to provide students with a common knowledge base of thetheory and operation of automotive systems and components. The Global Fundamentals Training Curriculum(FCS-13203-REF) consists of nine self-study books. A brief listing of the topics covered in each of the self-studybooks appears below.

Shop Practices (FCS-13202-REF) explains how to prepare for work and describes procedures for liftingmaterials and vehicles, handling substances safely, and performing potentially hazardous activities (such aswelding). Understanding hazard labels, using protective equipment, the importance of environmental policy,and using technical resources are also covered.

Brake Systems (FCS-13201-REF) describes the function and operation of drum brakes, disc brakes, mastercylinder and brake lines, power-assist brakes, and anti-lock braking systems.

Steering and Suspension Systems (FCS-13196-REF) describes the function and operation of the power-assisted steering system, tires and wheels, the suspension system, and steering alignment.

Climate Control (FCS-13198-REF) explains the theories behind climate control systems, such as heat transferand the relationship of temperature to pressure. The self-study also describes the function and operation of therefrigeration systems, the air distribution system, the ventilation system, and the electrical control system.

Electrical Systems (FCS-13197-REF) explains the theories related to electricity, including the characteristicsof electricity and basic circuits. The self-study also describes the function and operation of commonautomotive electrical and electronic devices.

Manual Transmission and Drivetrain (FCS-13199-REF) explains the theory and operation of gears.The self-study also describes the function and operation of the drivetrain, the clutch, manual transmissionsand transaxles, the driveshaft, the rear axle and differential, the transfer case, and the 4x4 system.

Automatic Transmissions (FCS-13200-REF) explains the function and operation of the transmission andtransaxle, the mechanical system, the hydraulic control system, the electronic control system, and the transaxlefinal drive. The self-study also describes the theory behind automatic transmissions including mechanicalpowerflow and electro-hydraulic operation.

Engine Operation (FCS-13195-REF) explains the four-stroke process and the function and operation of theengine block assembly and the valve train. Also described are the lubrication system, the intake air system,the exhaust system, and the cooling system. Diesel engine function and operation are covered also.

Engine Performance (FCS-13194-REF) explains the combustion process and the resulting emissions.The self-study book also describes the function and operation of the powertrain control system, the fuelinjection system, the ignition system, emissions control devices, the forced induction systems, and dieselengine fuel injection. Read Engine Operation before completing Engine Performance.

To order curriculum or individual self-study books, contact Helm Inc.Toll Free: 1-800-782-4356 (8:00 am 6:00 pm EST)Mail: 14310 Hamilton Ave., Highland Park, MI 48203 USAInternet: www.helminc.com (24 hours a day, 7 days a week)

Contents Introduction

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Introduction ................................................................................................................................. 1Preface ..................................................................................................................................................................... 1

Global fundamentals training overview ...................................................................................................... 1Contents ................................................................................................................................................................... 2

Lesson 1 Theory and operation of electriciy .......................................................................... 4General ..................................................................................................................................................................... 4

Objectives ....................................................................................................................................................... 4At a glance ............................................................................................................................................................... 5

Introduction .................................................................................................................................................... 5Components of electricity ............................................................................................................................. 5

Theory ...................................................................................................................................................................... 7Electron movement ........................................................................................................................................ 7

Operation ................................................................................................................................................................. 8Condutors and insulators .............................................................................................................................. 8

Lesson 2 Charateristics of electricity ..................................................................................... 9General ..................................................................................................................................................................... 9

Objectives ....................................................................................................................................................... 9Theory .................................................................................................................................................................... 10

Characteristics of electricity ........................................................................................................................ 10Factors that affect resistance ....................................................................................................................... 15

Operation ............................................................................................................................................................... 16Ohms Law ................................................................................................................................................... 16Watts .............................................................................................................................................................. 21

At a glance ............................................................................................................................................................. 22Units of measurements ................................................................................................................................ 22

Lesson 3 Complete electrical circuit ..................................................................................... 23General ................................................................................................................................................................... 23

Objectives ..................................................................................................................................................... 23At a glance ............................................................................................................................................................. 24

Complete electrical circuit .......................................................................................................................... 24Components ........................................................................................................................................................... 25

Components of a complete electrical circuit ............................................................................................. 25Generator ...................................................................................................................................................... 29Voltage regulator .......................................................................................................................................... 29Power distribution system ........................................................................................................................... 30

Operation ............................................................................................................................................................... 31Series circuits ............................................................................................................................................... 31Parallel circuits ............................................................................................................................................. 35

At a glance ............................................................................................................................................................. 38Common circuit faults ................................................................................................................................. 38

Introduction Contents

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Lesson 4 Basic control devices .............................................................................................. 40General ................................................................................................................................................................... 40

Objectives ..................................................................................................................................................... 40Components ........................................................................................................................................................... 41

Control devices ............................................................................................................................................ 41At a glance ............................................................................................................................................................. 49

Circuit protection ......................................................................................................................................... 49Components ........................................................................................................................................................... 50

Circuit protection (continued) .................................................................................................................... 50At a glance ............................................................................................................................................................. 54

Electromagnetic devices ............................................................................................................................. 54Components ........................................................................................................................................................... 55

Electromagnetic devices (continued) ......................................................................................................... 56Lesson 5 Wiring diagrams ..................................................................................................... 58General ................................................................................................................................................................... 58

Objectives ..................................................................................................................................................... 58At a glance ............................................................................................................................................................. 59

Wiring diagrams ........................................................................................................................................... 59Wire color codes .......................................................................................................................................... 59

Components ........................................................................................................................................................... 60Schematic symbols ...................................................................................................................................... 60Reading a wiring diagram ........................................................................................................................... 61

Lesson 6 Diagnostic process .................................................................................................. 62General ................................................................................................................................................................... 62

Objective ...................................................................................................................................................... 62At a glance ............................................................................................................................................................. 63

Symptom-to-system-to-component-to-cause diagnostic procedure diagnosis ...................................... 63Workshop literature ..................................................................................................................................... 64

List of abbreviations .................................................................................................................. 65

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General Lesson 1 Theory and operation of electricity

ObjectivesUpon completion of this lesson, you will be able to:

Explain the purpose and function of electricity.

Identify the components of electricity.

Explain the basic theory and operation of electricity.

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Lesson 1 Theory and operation of electricity At a glance

Introduction

Modern automobiles rely on a wide variety ofelectrical/electronic components and systems tooperate properly. Electricity plays a major role in theproper functioning of the engine, transmission, evenbrakes and suspension systems in many cases. Afundamental knowledge of how electricity works isimportant for any person associated with theautomobile repair industry.

Components of electricity

Matter, atoms and electrons

Electricity is defined as the flow of electrons througha conductor when a force is applied. To understandthis statement, we need to understand the structure ofmatter. Everything around us (solids, liquids, andgases) is considered matter. Matter is made frommany different atoms and combinations of atoms.

Atoms are made up of protons (which carry a positive[+] electrical charge), neutrons (which have noelectrical charge), and electrons (which carry anegative [-] electrical charge).

The nucleus, at the center of the atom, is made ofprotons and neutrons. Since protons have a positivecharge and neutrons have no charge, the nucleus itselfis positively charged. The negatively chargedelectrons orbit the nucleus, similar to the way theplanets in our solar system orbit the sun.

Construction of an atom

1 Nucleus (protons and neutrons)2 Electron orbit3 Electron

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At a glance Lesson 1 Theory and operation of electricity

Components of electricity (continued)Opposite electrical charges attract each other andsimilar electrical charges repel. The negativelycharged electrons stay in their orbit because they areattracted to the positively charged nucleus. Thisattraction is similar to the way the north (positive) andsouth (negative) poles of two magnets move towardeach other when placed closely together.

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Concept of attraction and repulsion

1 Unlike charges attract2 Like charges repel

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Lesson 1 Theory and operation of electricity Theory

Electron movement

Electron Flow

1 Nucleus2 Free electron3 Protons (positive charge)

An electron travels around the nucleus at exactly thespeed needed to hold its orbit. The balance betweenthe pull toward the nucleus and the centrifugal forceof the moving electron keeps each electron in itsrespective orbit (shell). The electrons in the outershell are called valance electrons. Valence electronsare further from the nucleus and easier to force out oforbit. When there is a good path or conductor,electrons can flow from one atom to another. Whenelectrons flow from one atom to another, electriccurrent flow exists.

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4 Free electron5 Atoms in conductor6 Electrons (negative charge)

An atom that is missing an electron is called apositive ion. An atom with an extra electron is calleda negative ion. Ions seek balance positive ions wantto gain an electron and negative ions want to get rid ofone. These attracting and repelling forces make up theelectrical pressure called Electromotive Force (EMF).Another name for EMF is voltage, which isdiscussed in greater detail later. Electrons flowingfrom one atom to another create electrical current.The ease or difficulty with which electrons flowthrough a material determines its classification aseither a conductor or insulator.

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Operation Lesson 1 Theory and operation of electricity

Conductors and insulators

Atoms are different from material to material. Themore valence electrons a material has, the harder it isto get them to move. Conversely, the fewer number ofvalence electrons, the easier it is to move them. Thedifference between a conductor and an insulator isdetermined by the number of valence electrons.

Conductors

A good conductor is any element that has less thanfour electrons in the outer shell. Copper is a commonconductor used in automotive wiring because it isstrong, relatively inexpensive, and has very littleresistance to electron flow. Other good conductorsinclude (in order from best to worst):

Silver

Gold

Aluminum

Tungsten

Iron

Steel

Mercury

Although silver and gold are the best conductors, theyare too expensive for common automotive use. Silverand gold are used only for critical applications. Sincegold resists corrosion, it is used on some automotiveconnectors.

Insulators

An insulator is any element that has more than fourelectrons in the outer shell. Insulators are materialsthat prevent or block current flow. The materialaround wires insulates the wire, protecting the wireand also preventing electrical shock. Some examplesof good insulators include:

Plastic

Glass

Rubber

Porcelain

Distilled water (although minerals in drinkingwater will conduct electricity)

Semiconductors

Semiconductors are elements that have exactly fourelectrons in the outer shell. Semiconductors onlyconduct electricity under very specific conditions.Semiconductors are used on printed circuit boards incomputers, radios, televisions, etc.

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Lesson 2 Characteristics of electricity General


Explain the characteristics of electricity.

Define Ohms Law.

Apply Ohms Law to solve for electrical values.

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Theory Lesson 2 Characteristics of electricity

Characteristics of electricity

Voltage

Voltage compared to a water tower

1 Difference of potential

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12-volt systems. Older vehicles use 6V, and sometrucks are 24V. With the addition of so manyautomotive electronic systems in todays modernvehicles, you can expect to see more and morepassenger cars operate with 24V and even 42V.

If you measure the voltage produced by a car battery,between the battery positive terminal and chassisground, you find that the difference between the twoterminals is what pushes current through the circuit,and the difference in this case is 12V.

Current cannot flow without voltage and a completepath to ground. Voltage and current work together tocreate power to get work done, such as illuminating alight bulb or making a motor run.

Voltage is the pressure (Electromotive Force) thatcauses current to flow through a conductor. The forceof voltage is created by a potential differencebetween two atoms, the difference between thequantity of positive (+) and negative (-) charges,which create an out-of-balance condition.

Voltage can be compared to hydraulic pressurecreated in a water tower. The pressure results from thepotential difference between the top of the tower(equivalent of 12 volts) and the bottom of the tower,or ground (equivalent of 0 volts).

Voltage is measured in units called volts, which iscommonly abbreviated as V. Most automotive circuitsoperate from the vehicles battery or generator and are

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Lesson 2 Characteristics of electricity Theory

Current

Current flow compared to water flow

1 Water flow2 Current flow3 Load

Using the water tower example, we can comparecurrent flow with the mass of water flowing from thetower to a faucet. Again, voltage is the potentialdifference between the negative and positiveterminals, and current is the actual flow or movementof electricity. In the water tower example, the actualflow of water from the tower to the ground is similarto electrical current flow. Keep in mind that currentonly flows when there is voltage (pressure) to force it.

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Current is the flow of electrons from one atom to thenext. Current is measured in amperes (amps),commonly abbreviated with the letter A. One ampmeans 6,280,000,000,000,000 (6.28 billion,BILLION) electrons passing a fixed point in onesecond. As an example of how powerful current is,less than one tenth of an amp flowing through thehuman body can cause serious bodily harm.

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Characteristics of electricity (continued)

Direct Current (DC)

Direct current occurs when there is a surplus ofelectrons at one battery terminal, resulting in a flow tothe other terminal where there is a scarcity ofelectrons. Direct current only flows in one direction.One advantage of DC is that it can be stored electro-chemically in a battery.

DC displayed as a scope pattern

1 Volts2 Time

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Alternating Current (AC)

Alternating current (AC) is produced when currentflows back and forth under the influence of changingpolarity (positive or negative). AC is constantlychanging its direction so that current first flows in onedirection (positive) one moment, and then in theopposite (negative) direction the next moment. This isreferred to as one cycle.

A cycle is usually represented as a sine wave becauseit follows the mathematical characteristics of a sinefunction. A cycle is one complete occurrence of thewave. The number of cycles per second is measuredin Hertz (Hz). This is also referred to as the frequencyof the AC current. AC displayed as a scope pattern

1 Volts2 Time3 Cycle

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Rectification

Since automotive electrical systems use DC voltage,the AC voltage generated by the generator must beconverted. Rectification is the process of convertingalternating current into direct current.

To rectify AC into DC, tiny semi-conductors calleddiodes are used. Diodes are devices that pass currentin only one direction, either positive or negative.Diodes are explained in greater detail later.

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Characteristics of electricity (continued)

Resistance

Resistance compared to restriction in water line

1 Resistance in a water line and in an electricalcircuit

Unwanted resistance in a circuit robs the circuit of itsfull current flow and causes the load to operateincorrectly or not at all. The more resistance in acircuit, the less current flow. The figure shownillustrates that resistance is like a bottleneck in a pipe.Resistance slows down or restricts the flow of current.Three factors that affect resistance are temperatureplus the length and diameter of the wire.

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Resistance opposes or restricts the flow of current in acircuit. All circuits have some resistance. Allconductors, like copper, silver and gold, have someresistance to current flow. We measure resistance inunits called ohms. The symbol for resistance is theGreek letter omega ().

Not all resistance is bad. In a normally operating lampcircuit, the lamp itself is usually the only measurablesource of resistance. The resistance in the lampsfilament resists current flow and heats up to the pointthat it glows.

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Factors that affect resistance

Temperature

Temperature affects different materials in differentways. For example, the resistance of copper and steelincreases as their temperature increases. When heat isapplied to these materials, their electrons maintaintighter orbits, making it more difficult for theelectrons to flow from one atom to another.

Size

A second factor that affects resistance is the size ofthe material used as a conductor. A larger conductormeans more electrons can flow through at the sametime. In smaller conductors, fewer electrons can flowthrough at the same time. When a wire is used as aconductor, the narrower the wire, the greater theresistance. As the diameter of the wire increases, theresistance decreases.

Length

The final factor is the length of the wire. As the lengthincreases, so does the resistance. This is becauseelectrons have to pass through more atoms. Electronstraveling through shorter wires encounter fewer atomsand less resistance.

Corrosion

Corrosion in a circuit also has an effect on resistance.Corrosion can result from exposure to the elementssuch as salt, water and dirt. If corrosion is present,resistance increases.

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Operation Lesson 2 Characteristics of electricity

Ohms Law

Ohms Law illustrated

Voltage, current, and resistance have a specificrelationship to each other. It is important tounderstand this relationship and be able to apply it toelectrical circuits, since this relationship is the basisfor all electrical diagnosis.

George Ohm, a scientist of the early 1800s, found thatit takes one volt of EMF to push one amp through oneohm of resistance. Current is directly proportional tothe applied voltage and inversely proportional toresistance in a basic circuit. Ohms Law is expressedas an equation that shows the relationship betweenvoltage (E for Electromotive Force), current flow(I for Intensity), and resistance (R):

E = I x R or Voltage = Amps x Resistance

The illustration shows a circuit with a 12 volt powersource, 2 Ohms of resistance and current flow of6 amps. If the resistance changes, so will current.

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Lesson 2 Characteristics of electricity Operation

Effect of increasing resistance

The illustration shows that resistance is increased to4 Ohms. Ohms Law states that current is inverselyproportionate to resistance. As shown, current isreduced to 3 amps.

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Ohms Law (continued)

Using the Ohms Law circle

An easy way to remember the basics of Ohms Law isto use the Ohms Law circle shown below. Thehorizontal line means divided by and the verticalline means multiply. Cover the letter representingthe value you are trying to determine.

If you know two of the three values for a givencircuit, you can find the missing one. Simplysubstitute the values for amps, voltage, and resistancein the equation, and solve for the missing value.

To determine:

Resistance cover the R. The resulting equationis: E/I (volts divided by amps = resistance)

Voltage cover the E. The resulting equation is:I x R (amps multiplied by resistance = voltage)

Current cover the I. The resulting equation is:E/R (volts divided by resistance = amperage)

It is important to understand that the letters used torepresent voltage and current may vary. For example,in some cases voltage is indicated simply with theletter V. In the Ohms Law explanation used herethe letter E means Electromotive Force, which isanother term for voltage. Additionally, current may berepresented by either the letter I, the letter A, orthe letter C.

Ohms Law circle (E = I x R)

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Effect of increasing resistance

In the illustration, resistance has increased to12 ohms. Current flow is reduced to 1 amp.

When voltage is constant:

current flow decreases when resistance increases.

current flow increases when resistance decreases.

When resistance is constant:

current flow increases when voltage increases.

current flow decreases when voltage decreases.

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Ohms Law (continued)

Applying Ohms Law

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Sample circuit for applying Ohms Law

Use the Ohms Law circle to solve the problem shownabove. The illustration shows a light bulb in a circuitthat has a current flow of 3 amps being pushed by 12volts. We want to determine the resistance. Hereshow you would work out this problem:

R = E / I

R = 12 volts/3 amps

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Ohms Law circle (E = I x R)

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Watts

Many electrical devices are rated by how much powerthey consume, rather than by how much they produce.Power consumption is expressed in watts.

746 watts = 1 imperial horsepower735 watts = 1 metric horsepower

The relationships among power, voltage, and currentare expressed by the Power Formula:

P = E x I

In other words, watts equals volts multiplied by amps.

For example, if the total current in a circuit is 10amps and the voltage is 120 volts, then:

P = 120 x 10P = 1200 watts

In a circuit, if voltage or current increases, then powerincreases. If voltage or current decreases, then powerdecreases. The most common application of a ratingin watts is probably the light bulb. Light bulbs areclassified by the number of watts they consume.

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At a glance Lesson 2 Characteristics of electricity

Units of measurements

Electrical values are often very large or very small.Electrical values are indicated by metric numbers.The metric measurements used are Mega, Kilo, Milli,and Micro.

Mega (M) means one million. For example, a circuitwith one million ohms of resistance can be written as1,000,000 Ohms. If the decimal is moved to the left,the value can be written as 1 Megohm, or 1 M.

Kilo (K) stands for one thousand. A circuit withtwelve thousand volts can be written as 12,000 volts.Or, with the decimal moved three spaces to the left, itcan be written as 12 Kilovolts, or 12 Kv.

Milli (m) means one thousandth. A circuit with 0.015amperes of current can be written as 0.015, or bymoving the decimal three places to the right, it can bewritten as 15 Milliamperes, or 15 mA.

Micro () means one millionth. For explanationpurposes, assume that there is a circuit with 0.000015amperes. By moving the decimal six places to theright, this can now be written as 15 microamperes, or15 a.

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Lesson 3 Complete electrical circuit General


Describe a complete circuit.

Identify the components of a complete circuit.

Identify basic types of circuits.

Explain the theory and operation of a complete circuit.

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At a glance Lesson 3 Complete electrical circuit

Complete electrical circuit

Electricity is current flowing through a completecircuit. A typical modern vehicle may contain over1,000 individual electrical circuits. Some are verycomplicated, but they all operate on the same basicprinciples.

In order for a complete circuit to exist, there must bea power source, a conductor, a load, and ground. Mostautomotive circuits include:

Power source (battery or generator)

Conductor (wire or cables)

Ground path (car chassis and battery ground cable)

Load (light bulb or motor)

Protection device (fuse or circuit breaker)

Control device (switch or relay)

Regardless of the number or location of components,current always flows in a complete loop. Inautomotive circuits, current flows from the powersource, through the electrical load, and back toground. The illustration shows the path currentfollows in a typical automotive circuit.

Typical automotive electrical circuit components

1 Power source2 Conductor3 Fuse4 Switch5 Load6 Chassis ground

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Lesson 3 Complete electrical circuit Components

Components of a complete electrical circuit

Conductor

Any material that allows current to flow easily is aconductor. The use of copper as a commonautomotive conductor, and some of the factors thataffect how well a conductor works were discussedpreviously.

Voltage source

The voltage source in a circuit supplies voltage, orelectrical pressure. Automotive power sources arebatteries and generators.

Load device in a circuit

Load device

A load converts current flow into heat, light, ormotion. Examples of loads include rear windowdefoggers (heat), light bulbs (light), and motors(motion). As shown, the symbol for the loadrepresents a headlamp, or other illumination device.

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Components Lesson 3 Complete electrical circuit

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Components of a complete electrical circuit (continued)

Body ground

Control devices

Control devices, such as switches or relays, make acircuit more usable by allowing current to be turnedon and off at specific points in the circuit. A closedswitch in a circuit completes the path and allowscurrent to flow. Opening the switch breaks the path,and stops current flow.

In a simple circuit, the location of the switch makesno difference. If the path is broken, current cannotflow, as shown. Even if the switch is positioned on theground side of the switch, the bulb will not illuminateunless the circuit is complete.

Effect of an open switch

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Ground path

Ground completes the path back to the voltage source.Voltage is at its lowest potential when it is on theground side of the circuit. On most vehicles, thenegative side of the battery connects to ground.

In a vehicle, it is not practical to have separate groundwires returning to the battery for each system. Abody ground completes most automotive circuits.Body grounds use the vehicles body, engine, or frameas the return path to the voltage source. The steel inthese parts of the vehicle provides an excellent returnpath for electrical current.

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Circuit protection devices

Each electrical circuit contains one or more circuitprotection devices to prevent damage to electricalwiring and electronic components. These devices canbe fuses, fusible links, circuit breakers, or acombination of these.

Battery and schematic symbol

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Fuse and schematic symbol

Battery

During starting, the battery supplies electricity to thestarter motor, ignition, and fuel system components.The battery provides all vehicle power when theengine is off. Once the vehicle is running, the batteryserves as an additional electrical source when vehicledemands temporarily exceed the output of thecharging system.

A battery produces electricity through a chemicalreaction between positive and negative platessubmerged in a solution of sulfuric acid and water.The illustration shows the battery plates and theschematic symbol for a battery.

When the battery is fully charged, the chemicaldifference between the positive and negative plates ishigh. There is a surplus of electrons at one of theterminals. As the battery discharges, the platesbecome more alike the potential difference (voltage)drops.

Charging a battery produces a chemical reaction thatincreases the potential difference of the plates. A fullycharged battery outputs between 12.7 and 12.9 volts.

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Components of a complete electrical circuit (continued)Battery (continued)

Automotive batteries are manufactured in varioussizes to meet the needs of many different applications.The capacity of the battery is usually given in coldcranking amps (CCA). Cold cranking amps indicatethe amount of current the battery can deliver at-17.8C (0F) for 30 seconds while maintaining 7.2volts, and after 90 seconds maintaining 6V.

In some regions of the world, batteries are rated inampere-hours. Ampere-hours refers to how muchcurrent the battery can deliver during 20 hours at25C (77F) while maintaining 10.5V. A 100 ampere-hour battery can deliver 5A during 20 hours. Theaverage automobile battery has a capacity ofapproximately 60 ampere-hours.

The two common types of batteries used inautomobiles are low maintenance andmaintenance-free. Maintenance-free batteries arecompletely sealed and do not require addition ofwater. Low maintenance or standard lead batteries arenot sealed and require periodic water level inspection.

Reserve capacity

The reserve capacity is determined by the length oftime in minutes that a fully charged battery can bedischarged at 25 amperes before battery cell voltagedrops below 1.75 volts per cell. The reserve capacityrating gives an indication of how long the vehicle canbe driven, with the headlights on, if the chargingsystem should fail.

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Generator

A generator converts an engines mechanical energyinto usable electrical energy. The generator producesAC by a principle called electromagnetic induction.A conductor moving through a magnetic field createsmagnetic induction. Because generators produce AC,an internal rectifier changes the current from AC toDC, as mentioned previously.

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Typical AC generator

Voltage regulator

A voltage regulator maintains voltage to the batteryrecharging circuit at a predetermined level,eliminating power surges and overloads from thegenerator. Since the generator connects directly to thebattery, an overload could cause a fire. Todaysvoltage regulators are an integral part of the generator.In vehicles manufactured before the mid 1970s, thevoltage regulator was usually a separate unit.

When the generator produces enough current torecharge the battery, the voltage regulator opens theflow to the battery recharging circuit and monitors thevoltage. Generally, a 12-volt battery requires about14.0 volts of input to recharge. When the generatorslows down or stops, the voltage regulator halts flowto the battery recharging circuit.

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Power distribution center

1 Internal connectors2 Relays3 High current fuses

Power distribution system

Power distribution usually begins at the powerdistribution box in a vehicle. The high-current powerdistribution box contains high-current fuses and maybe located under the hood near the battery. The low-current fuses are usually in a fuse junction panelwhich can be located just about anywhere on thevehicle, depending on manufacturer. Both aredesigned to hold fuses and supply power to severalcircuits.

In modern vehicles, the fuse block is arranged withcircuits directly from the battery and others that arecontrolled by the ignition switch. To reduce thenumber of wires at the fuse block, a single batterycircuit and a single ignition circuit may be connectedto a bus bar to distribute power to numerous systemsthrough several fuses.

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Lesson 3 Complete electrical circuit Operation

Voltage and voltage drop

Components or loads in a complete circuit mustconsume a certain amount of voltage to operate.Voltage drop describes the voltage that is used up asit passes across the load. A voltage drop occurs onlywhen current is flowing.

The dropped voltage (energy) is converted to heat ormotion. In the case of a simple lamp circuit, thevoltage dropped across the lamp causes it toilluminate (voltage converted to heat). If additionalloads or lamps are in series, the voltage drops acrosseach device proportionally.

The load with the most resistance drops the mostvoltage, and the total voltage drop in a series circuitequals the source voltage.

Sometimes a voltage drop represents a defect in thecircuit. For example, the resistance caused bycorroded wires or connectors can consume voltageoriginally intended for the load.

Voltage should always be near zero (less than0.1 volt) on the ground side of the last load.

Series circuits

A series circuit is one in which there is only onecomplete path for current to flow. As shown, when theswitch in the circuit is closed, current only has onepath to follow. Series circuits are the simplest type ofelectrical circuits.

Simple series circuit

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Operation Lesson 3 Complete electrical circuit

Series circuits (continued)

Voltage drop in a series circuit

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Voltage drop (series circuit shown)

In series circuits, voltage drops proportionately acrosseach load when current is flowing. Adding loads tothe circuit decreases the available voltage. Forexample, adding an extra lamp in series causes alllamps to get dim.

In a circuit with one load, the single load shouldconsume all the source voltage. If you measure thevoltage, you see 12V before the load and 0V after.The load consumes all 12 volts.

In a circuit with two loads, equal loads share thevoltage. In the figure shown, if you measured thevoltage before the first load, you would see 12V.

After voltage was dropped across the first load, youwould see 6 volts remaining for the second load. Thisvoltage is dropped across the last load, leaving 0volts. Each load dropped 6 volts. If you add all thevoltage drops, the total is 12V (6V + 6V = 12V). Thetotal of all voltage drops must equal the sourcevoltage.

Adding loads in series decreases the voltage availableto each load, and reduces current flow in the circuit.For example, adding lamps causes all lamps to dim.When a switch is open in a circuit, source voltage ispresent, but current cannot flow. Part of a circuit canhave voltage even though no current is flowingthrough the circuit.

Service Training 33


Current in a series circuit

Current (series circuit shown)

In a series circuit, there is only one path for currentflow. Current passes through each load and returns tothe battery through ground. Because there is only onepath for current in a series circuit, a break anywherein the circuit (a break is known as an open circuit)stops current flow.

ELEC068-AVF

2A2A 2A 2A

12V

Each load has some resistance to current flow. Themore loads you connect in series, the higher the totalresistance in the circuit and the lower the current flow.This means the amount of current flow in a circuitdepends on the amount of source voltage as well asthe circuit resistance.

34 Service Training


Series circuits (continued)

Resistance in a series circuit

Resistance (series circuit shown)

To determine the total resistance in a series circuit,add the individual resistances together. It does notmatter where the resistance is located in the circuit.For example, the circuit shown has a total resistanceof 18 ohms. The calculation is 10 + 8 = 18 .

ELEC027-AVF

12V

Service Training 35


Parallel circuits

Basic parallel circuit

A parallel circuit is one in which there is more thanone path for current to flow. Although voltage, currentand resistance still affect parallel circuits, their effectis different from a simple series circuit.

In parallel circuits, each branch has battery voltage.Adding branches does not decrease available voltage.In other words, each branch of a parallel circuit actslike a separate series circuit.

Most automotive circuits are parallel. Parallel circuitshave one great advantage: if one of the loads orbranches develops high resistance, the other branchesstill operate normally.

ELEC030-AVF

12V

12V 0V

12V 0V

Voltage in a parallel circuit

The voltage applied to each branch of a parallelcircuit is the same as the source voltage. The voltagedrop across each of the loads in the figure shown isequal also.

36 Service Training


Parallel circuits (continued)

Current in a parallel circuit

ELEC031-AVF

12V

4A

6A

2A

Current (parallel circuit shown)

When a circuit contains more than one path, currentflow may be different in each branch (depending onthe resistance of each branch), but the voltage to eachbranch does not change.

The figure shows a typical parallel circuit. Currentdivides into two branches at the splice, and eachbranch has its own load and separate ground path. Inparallel circuits, total current flow is equal to thecurrent flow of all branches added together. So in thissample circuit, total current flow equals 4A + 2A, or6A. If one branch of a parallel circuit develops highresistance, the other branches are not affected.

In a parallel circuit, adding more branches and loadsin parallel increases total current flow because thereare more paths for current to follow.

This characteristic of parallel circuits explains whyinstalling aftermarket devices can cause problems.Incorrectly splicing these devices (stereos, alarms,etc.) into existing circuits may increase current flowto the point that the circuit fuse blows.

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Resistance in a parallel circuit

Resistance (parallel circuit shown)

Calculating the total circuit resistance in parallelcircuits is a little more difficult. Finding total circuitresistance in parallel circuits may not be practical, soit is best to simply remember that in parallel circuits,the total circuit resistance is less than the resistance ofthe smallest individual resistance. For example, in thefigure shown, the smallest resistance value is 6 ohms,but the total circuit resistance is 4 ohms.

The actual calculation is done by taking the sourcevoltage for the circuit and dividing it by the combinedcurrent draw of each branch. The source voltage is12V. The current draw is 2A for one branch, and 1Afor the other. The total circuit draw is 1A + 2A = 3A.12V / 3A = 4 ohms total circuit resistance.

ELEC032-BVF

6

12

12V 3A

2A

1A

38 Service Training

At a glance Lesson 3 Complete electrical circuit

Common circuit faults

Short-to-ground

A short-to-ground is an unwanted path between thepositive and ground side of a circuit. When thishappens, current flows around the intended loadbecause electrical current always tries to flow throughthe path of least resistance.

Since the resistance produced by a load reduces theamount of current flowing in a circuit, a short mayallow a very large amount of current to flow.Excessive current flow normally opens (or blows) thefuse. In the figure, the short bypasses both the openswitch and the load, and goes directly to ground.

Short-to-power

A short-to-power is also an unplanned path for currentflow. In the figure shown, a path flows around theswitch in the circuit directly to the load. This causesthe bulb to illuminate, even though the switch is open.

Short to ground

ELEC020-AVF

ELEC021-AVF

Short to power

Service Training 39

Lesson 3 Complete electrical circuit At a glance

Open circuit

Removing either the voltage source or the ground sideconductor breaks a circuit. Because there is no longera complete path, current does not flow, and the circuitis open. In the figure shown, the switch opens thecircuit and stops the flow of current.

Open Circuit

Examples of opens

1 Blown fuse2 Disconnected from voltage source3 Broken wire4 Disconnected from ground5 Burned out bulb

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3

5

4

ELEC022-AVF

Some opens are planned, while others areunintentional. The figure shows some examples ofunplanned opens.

40 Service Training

General Lesson 4 Basic control devices


Describe common electrical/electronic devices.

Identify the types of common electrical/electronic devices.

Explain the theory and operation of common electrical/electronic devices.

Describe common solid state devices.

Identify the types of common solid state devices.

Explain the theory and operation of common solid state devices.

Describe common electrical/electronic circuit protection devices.

Identify the types of common electrical/electronic circuit protection devices.

Explain the theory and operation of common electrical/electronic circuit protection devices.

Describe common electrical/electronic electromagnetic devices.

Identify the types of common electromagnetic devices.

Explain the theory and operation of common electromagnetic devices.

Service Training 41

Lesson 4 Basic control devices Components

Control devices

Switches

Switches serve as OFF/ON devices in a circuit byopening or closing the circuit. Switches can bemanually controlled or operated automatically, basedon a circuit or vehicle condition.

Switches can be normally open (NO) or normallyclosed (NC). Normally open means the at-restposition of the switch opens the circuit. Normallyclosed means the at-rest position of the switch closesthe circuit.

A hinged pawl switch is the simplest type of switch.It either opens or closes the circuit.

Simple switch

1 In2 Hinged pawl switch3 Wiper4 Contact5 Out

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2

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Single Pole, Single Throw (SPST) switch1 In2 Out

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2

Switches have one or more poles (inputs) and throws(outputs). For example, a single-pole, double-throwswitch has one input and two outputs. A gangedswitch has two or more wipers that operate in unison(mechanically linked) from a single control. Thefollowing illustrations show three types of switches.

42 Service Training

Components Lesson 4 Basic control devices

Single Pole, Double Throw (SPDT) switch1 In2 Out3 Out

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1

3 2

Control devices (continued)

Double Pole, Double Throw (DPDT) switch1 In2 Out3 Out

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1

23

Service Training 43


Momentary contact switch

The momentary contact switch has a spring-loadedcontact; the spring keeps the contact from completingthe circuit.

A typical example of a momentary contact switch isthe horn button. When the button is pressed, the hornsounds. Releasing the button breaks the contact andthe sound stops.

Momentary contact switch operation

1 Operation button2 Spring3 Horn (load)4 Contacts5 From power source

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5

4

21

3

44 Service Training



Diodes

A diode is a semiconductor device used to preventcurrent flow in an undesired direction or path. Diodesare often made of specially modified silicon that actsas an insulator until enough voltage of the correctpolarity is applied. When voltage is present in thecorrect direction (polarity), the diode changes to aconductor and current flows in the circuit. If theapplied voltage or current flows in the wrongdirection, the diode remains an insulator and blockscurrent flow.

There are many different types of diodes used inautomotive applications. Diodes are used for:

rectification changing AC to DC

controlling voltage spikes and surges that couldcause damage to solid state circuits

indicators on instrument panels

voltage regulation

Regular diode and symbol

1 Positive (anode)2 Negative (cathode)

ELEC069-B/VF

+

1 2

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Capacitor

Capacitors absorb or store electrical charges. Thecapacitor is made of two or more conducting plateswith non-conducting material between them. Directcurrent cannot flow through a capacitor, butalternating current can.

The slight flow of direct current that does occur isuseful in soaking up voltage spikes, preventing arcingacross opening contacts. Capacitors also serve asnoise filters when used in audio applications.Capacitors are rated in units called Farads (F).

Capacitor and symbol

ELEC046-B/VF

46 Service Training



Transistors

Transistors are semiconductor devices with threeleads. A very small current or voltage at one lead cancontrol a much larger current flowing through theother two leads. This means transistors can be used asamplifiers and switches.

The three layers of a transistor are the emitter, baseand collector. The base is very thin and is lessconductive than the emitter and collector. A verysmall base-emitter current causes a much largercollector-emitter current to flow.

NPN transistor and symbol

1 Negative2 Positive3 Negative4 Collector (c)5 Base (b)6 Emitter (e)

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N

N

P2

1

4

5b

c

e

6

3

Service Training 47


Though there are many different types of transistors,the most common used in automotive circuits is theNPN (negative-positive-negative) transistor.

When the voltage difference between the base-emitteris less than 0.6V, the transistor is closed. If the voltagedifference is increased to 0.6V the transistor opens,and current flows through the load and through thetransistor from collector to emitter. The amount ofcurrent is dependent on the amount of current flowingfrom base to emitter.

NPN transistor used in a circuit

1 Direction of current flow

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12 V

1b

c

e

48 Service Training


NPN transistor and symbol

1 Positive 4 Collector (c)2 Negative 5 Base (b)3 Positive 6 Emitter (e)

Control devices (continued)Another type of transistor is the PNP. A PNPtransistor operates similar to an NPN transistor excepta PNP transistor opens when the voltage differencebetween the emitter and base is 0.6V.

ELEC072-A/VF

P

P

N2

1

4

5

6

3

b

e

c

ELEC102-A/VF

12 V

bc

e

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Lesson 4 Basic control devices At a glance

Circuit protection

Circuit protection devices

Common circuit protection devices (not actual size)6 Blown fuse7 Circuit breaker8 Bi-metal arm9 Contacts

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1

87

9

1 Small wire2 Splice3 Circuit conductor4 Fusible link5 Good fuse

In some instances, high current flow can exist in acircuit. Without some means of protecting the circuit,a short allows the total amount of available current toflow. If the current is more than the circuit wasdesigned to carry, the wiring may overheat and burn.

Each electrical circuit contains one or more circuitprotection devices to prevent damage to electricalwiring and electronic components. These devices canbe fuses, fusible links, circuit breakers, or acombination of these. Some computers on anautomobile protect themselves by shutting down in anoverload or when voltage exceeds specifications.

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Circuit protection (continued)

Fuses

Types of fuses

1 Cartridge fuse2 Maxifuse

3 Standard blade type fuse4 Miniature blade type (minifuse)

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1 2 3 4

Fuses are plug-in devices with two terminalsconnected by a conductor that is designed to melt(blow) when a specified amperage rating is exceeded.Fuses must be replaced after the circuit problem hasbeen corrected.

There are basically four types of fuses: the cartridgefuse, high-current (or maxifuse), the standard bladetype, and the miniature blade type. Blade type fusesare the most common and have a specific amperagerating and are color-coded. They are permanentlymarked with the amperage rating and the voltagerating. Two slots in the fuse body allow the technicianto check for voltage drop, available voltage, orcontinuity.

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Fuse in a circuit used as a protection device

ELEC018-A/VF

Fuses are constructed so that if current reaches acertain level, the metal melts and breaks, causing anopen in the circuit. This opens the circuit and protectscircuit wiring and components from excessive currentflow.

Fuses are rated by amperage handling ability. Forexample, a 10 amp fuse opens if current in the circuitincreases too far above 10 amps for a certain length oftime.

Never replace a fuse with a higher rated fuse. Alwaysconsult the workshop manual or owner manual to besure that you replace each circuit protection devicewith the exact equivalent specified.

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2

43

1

Fusible link construction

1 Small wire2 Splice3 Circuit conductor4 Fuse link burn out in this area when too much

current flows through

Fusible links

The fusible link is installed close to the voltagesource. The fusible link usually protects large portionsof the vehicle wiring where fuses or circuit breakersare not practical. If an overload occurs, the lightergauge wire in the fusible link melts and opens thecircuit before damage can occur.

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Cycling circuit breaker construction

1 Side view (external)2 Bi-metal arm3 Side view (internal)4 Contacts

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2 31

Circuit protection (continued)

Circuit breakers

A circuit breaker can be a separate plug-in assemblyor can be mounted in a switch or motor brush holder.A set of contacts inside these devices opens the circuittemporarily when a specified amperage rating isexceeded.

Unlike fuses, circuit breakers do not have to bereplaced each time they open. However, if a circuitopens, the cause of the overload or short in the circuitmust still be found and repaired, or further damage tothe circuit results.

Generally, there are two types of circuit breakers cycling and non-cycling.

Cycling circuit breakers

The cycling circuit breaker contains a strip built fromtwo different metals. Each metal expands at adifferent rate when heated. When an excessiveamount of current flows through the bi-metal strip,the high-expansion metal bends due to the heat build-up and opens the contact points. With the circuit openand no current flowing, the metal strip cools andshrinks until the contact points again close the circuit.

In actual operation, the contact opens very quickly.If the overload is continuous, the circuit breakerrepeatedly cycles (opens and closes) until thecondition is corrected.

Service Training 53


Non-cycling circuit breakers

A non-cycling circuit breaker uses a wire coilwrapped around a bi-metal arm which maintains ahigh-resistance current path in the circuit even afterthe contact points open. The heat from the wire coildoes not allow the bi-metal strip to cool enough toclose the contact points until the source voltage isremoved from the circuit.

When voltage is removed, the bi-metal strip cools andthe circuit is restored. With a non-cycling circuitbreaker, once the breaker opens the circuit, voltagemust be removed from the circuit to reset the breaker.A non-cycling of circuit breaker cannot be used incrucial circuits such as headlamps, because atemporary short terminates the circuit voltage untilthe breaker can be reset.

Non-cycling circuit breaker construction

1 Side view (external)2 Contacts3 Side view (internal)4 Coil5 Bi-metal arm

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3

5

54 Service Training

At a glance Lesson 4 Basic control devices

Electromagnetic devices

Many electrical devices operate on the principle ofelectromagnetic induction. Electromagnetic inductionis the process of producing electrical current in aconductor as the conductor passes through a magneticfield or another current-carrying conductor, such as acoil.

Relays, motors, generators and solenoids areexamples of electromagnetic devices.

Relays

A relay is an electric switch that uses a small currentto control a larger current. Relays consist of a controlcircuit, an electromagnet, an armature, and a set ofcontacts, as shown.

Applying a small current to the control circuitenergizes the electromagnet which moves thearmature. The movement of the armature either opensor closes the contacts mounted on the armature.

Relay

1 From power source2 From power source3 Normally closed contact4 To load5 Ground (control circuit)

ELEC061-A/VF5 4 3

21

Service Training 55


When the control circuit for the relay is closed, theelectromagnet draws the armature toward the core.This closes the contact points and provides the largercurrent for the load. When the control switch is open,no current flows to the relay coil. The electromagnetis de-energized and the armature returns to its normal,or rest position.

There are many automotive applications for relaysincluding the fuel pump, horn, and starter system.

Application of a relay

1 From ignition switch2 From battery3 Fuel pump relay4 Fuel pump motor5 Powertrain control module6 Fuel pump relay control

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1 2

4

3

56

M

56 Service Training


Electromagnetic devices (continued)

Solenoids

Solenoid operation

1 Voltage source2 Momentary contact switch3 Trunk latch

4 Core or plunger5 Ground

Solenoids are electromagnets with a moveable core orplunger. The core or plunger converts electricalcurrent flow into mechanical movement. The figureshows a typical automotive solenoid application, theremote latch mechanism in the luggage compartment.

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2

1

3

45

Service Training 57


Motors

Motor operation

1 Permanent magnet2 Armature3 Commutator

4 Battery5 Conductor

Motors are devices that convert electrical energy intomechanical motion. Electric motors can meet a widerange of service requirements that include starting,accelerating, running, braking, holding, and stoppinga load.

The figure shows the construction of a simple DCmotor which consists of a horseshoe-shapedpermanent magnet with a wire-wound coil (armature),mounted so it can rotate between the north and southpoles of the magnet. The commutator reverses thecurrent fed to the coil on each half-turn. The armaturerotates due to the force exerted on a conductorcarrying the current in a magnetic field.

ELEC043-A/VF

1 1

22

5 5

4 4

33

58 Service Training

General Lesson 5 Wiring diagrams


Explain the purpose of automotive wiring diagrams.

Identify wiring diagram symbols and which electrical components they represent.

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Lesson 5 Wiring diagrams At a glance

Wiring diagrams

A wiring diagram shows all the wiring, components,and grounds of a vehicles electrical system in detail.A wiring diagram is like a road map of the vehicleselectrical system, showing how all the circuits andcomponents are connected. You should always refer tothe wiring diagram for the proper procedure to trace afault and to remove and repair connectors.

Wire color codes

Wiring used in automotive electrical systems is color-coded for identification. Each wire on the wiringdiagram has a code letter placed next to it. Thesecodes help you identify the correct wire on thevehicle.

Wires are not always one color. Two-color wires aretypically indicated by a two-letter symbol. When awiring diagram shows two code letters, the first letteris the basic wire color, and the second letter is thecolor of the marking (stripes, dots, or hash-marks) onthe wire.

For example, a wire labeled B/R is black with redmarking. A GY/O wire is gray with an orange stripeor marking. A black wire with a white stripe isdesignated B/W. Always refer to the wiring diagramfor the current information on wire color codes.

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Components Lesson 5 Wiring diagrams

Schematic symbols

Common wiring diagram symbols

You are already familiar with common electricalschematic symbols such as chassis ground, battery,fuses, and switches. Wiring diagrams use even moresymbols to represent electrical system components.

To read and use a wiring diagram successfully, youmust be able to identify electrical component symbolsand their meanings. The following graphic showssome of the additional schematic symbols commonlyused in wiring diagrams.

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Lesson 5 Wiring diagrams Components

Reading a wiring diagram

Always read and analyze the wiring diagram beforeattempting to repair an electrical problem. Carefullyanalyzing the circuit and being able to predict itsnormal operation saves time and effort. Knowingwhere to make measurements helps avoid removingand replacing components unnecessarily.

Use the following procedure to read a wiring diagram:

1. Make sure you have the correct wiring diagramfor the vehicle you are working on.

2. Carefully review the General Informationsection to familiarize yourself with the wirecolor codes, common connectors, groundpoints, etc.

3. Locate the wiring diagram section that containsthe problem circuit or component. Find thecomponents ground point and follow thecircuit up to its power source. Make sure youcan trace the complete circuit path from thepower source through all fuses, switches,relays, etc., to the component and back to thepower source through the ground.

4. Determine if the circuit is in series, parallel,switch-to-ground, load-to-ground, etc.Determine the direction of current flow in thecircuit.

5. Predict the normal operation of the circuit.Divide the circuit into smaller sections andlocate a convenient point to test the circuit orsuspected problem component.

6. Find the test point on the vehicle and predictthe voltage, current, or resistance at the testpoint. Test the circuit using the appropriatetesting device (ohmmeter, voltmeter, ammeter,etc.). Do the test results match your predictedcircuit operation values or the specifications inthe Workshop Manual?

62 Service Training

General Lesson 6 Diagnostic process

ObjectiveUpon completion of this lesson you will be able to:

Explain the Symptom-to-System-to-Component-to-Cause diagnostic procedure and provide an example.

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Lesson 6 Diagnostic process At a glance

Symptom-to-system-to-component-to-cause diagnostic procedure diagnosis

Diagnosis requires a complete knowledge of thesystem operation. As with all diagnosis, a technicianmust use symptoms and clues to determine the causeof a vehicle concern. To aid the technician whendiagnosing vehicles, the strategies of many successfultechnicians have been analyzed and incorporated intoa diagnostic strategy and into many servicepublications.

Symptom-to-system-to-component-to-causediagnostic method

Using the Symptom-to-System-to-Component-toCause diagnostic routine provides you with a logicalmethod for correcting customer concerns:

First, confirm the "Symptom" of the customersconcern.

Next, you want to determine which System onthe vehicle could be causing the symptom.

Once you identify the particular system, you thenwant to determine which Component(s) withinthat system could be the cause for the customerconcern.

After determining the faulty component(s) youshould always try to identify the cause of thefailure.

In some cases parts just wear out. However, in otherinstances something other than the failed componentis responsible for the problem.

1 Symptom2 Vehicle systems3 Components4 Causes

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At a glance Lesson 6 Diagnostic process

Symptom-to-system-to-component-to-cause diagnostic procedure diagnosis (continued)Symptom-to-system-to-component-to-causeprocess example

An example of the Symptom-to-System-to-Component-to-Cause diagnostic routine in use ishighlighted in this example. As you read thisexample, the steps in the process and how they relateto finding the actual cause of the concern are stated.

The first step of the diagnostic process is verifying thesymptom(s) of the concern. A customer brings avehicle in for service because of a concern regardingan inoperative speedometer. A test drive verifies theconcern. The test drive validates the Symptomportion of the diagnostic process.

The next step in the diagnostic process is to isolatethe system(s) that are affected by the symptom.Visual inspection does not show any obvious signsrelating to the wiring, connectors, and the vehiclespeed sensor. Using the appropriate electronicdiagnostic equipment, diagnostic trouble codeinformation indicates a problem with the controllingcomputer for the vehicle speed signal. The test dataprovided in the manual validates the System portionof the diagnostic process.

Next in the diagnostic process is to isolate thecomponent(s) that relate to the system and symptom.In this case, the vehicle speed signal goes from thesensor to the Powertrain Control Module (PCM) andthe PCM sends the signal to the instrument cluster.Using the procedures in the appropriate workshopmanual, the vehicle speed sensor is identified asgiving faulty input to the PCM. The sensor is thecomponent at fault. Following the workshop manualprocedures provides validation of the Componentportion of the diagnostic process.

Finally, the diagnostic process determines what theCause of the component failure is. In this case atest of the sensor finds faulty internal circuitry withinthe sensor. This validates the Cause relating to thecomponent failure.

Replacing the sensor returns the vehicle to properoperating condition.

Workshop literature

The vehicle workshop literature contains informationfor diagnostic steps and checks such as: preliminarychecks,verification of customer concern/specialdriving conditions, road tests and diagnostic pinpointtests.

Service Training 65

List of abbreviations Electrical systems

A Amps, amperage amperes or C or I

AC Alternating Current

C Current or Amps or Intensity

C Celsius

DC Direct Current

DPDT Double Pole, Double Throw

E Volts or V or electromotive force or U

EMF Electromotive Force or volts orV or E

F Farads

F Fahrenheit

Hz Hertz

I Intensity or current flow or A or C

k Kilo or one thousand

LED Light Emitting Diode

M Mega or one Million

m Milli or one thousandth

NC Normally Closed

NO Normally Open

NPN Negative, Positive, Negative

Orbit Shell

P Power or watts

PNP Positive, Negative, Positive

PTC Positive Thermal Coefficient

R Resistance, or ohms, or

Shell Orbit

SPDT Single Pole, Double Throw

SPST Single Pole, Single Throw

U Units is voltage

V Volts, or voltage or electromotiveforce or U

W Watts

micro or one millionth

Omega, or ohms, or R

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