© 2012 Delmar, Cengage Learning Lighting and Wiring Service Chapter 33.
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Transcript of © 2012 Delmar, Cengage Learning Lighting and Wiring Service Chapter 33.
© 2012 Delmar, Cengage Learning
Objectives• Diagnose problems in lighting and wiring
systems• Adjust headlamp aim• Make repairs to automotive wiring, lamps and
bulbs, and protection devices
© 2012 Delmar, Cengage Learning
Analyzing Electrical Problems• Diagnose problem cause
– Verify the complaint
– Check for related symptoms
– Check wiring diagram for common problems
• Problem types– Open circuit: break in continuity
– Short circuit: unwanted current path• Grounded circuit: short circuit to ground
– Excessive resistance: reduces current flow• Corroded connector is a common cause
© 2012 Delmar, Cengage Learning
Wiring Service• Wiring diagrams: road maps to electrical circuits
– Wires are numbered or colored• First color is insulation; second is stripe• Numbers refer to wire gauge or locations
– Letters preceding the number • G: grounds• S: splices• C: connectors
– SAE wiring diagrams• Arranged so upper right is power feed• Lower right is ground
© 2012 Delmar, Cengage Learning
Crimp Terminals• Install terminal on wire
– Strip about ¼ inch of insulation from end of wire
– Insert wire end into terminal and crimp • Poor crimp creates excessive resistance• W-crimp crimps longitudinally
• Terminal block keeps wires organized– Depress locking tang to remove terminals
• Crimp connectors splice wires together– Insert both ends into connector and then crimp
– Wires should be side by side
© 2012 Delmar, Cengage Learning
Selecting Replacement Wire• Replacement wire and cable
– Comes wound in spools
– Use wire adequate for load
– Replacement wire should be at least as big as original
– Wire that is too small or too long causes excessive resistance
– Doubling the length doubles the resistance
© 2012 Delmar, Cengage Learning
Adding Electrical Accessories• Aftermarket accessories
– Usually require separate fused circuit
• Fuse holders– Original equipment accessories take power from
a fuse on the fuse panel• Fuse holder can be connected to existing power
source• Tap splice connectors are used in electrical
circuits only, not in electronic circuits
© 2012 Delmar, Cengage Learning
Soldering• Preferred for electronic circuits
– Small amount of current runs through
– Does not suffer increased resistance due to oxidation
• Soldering iron is used for wiring connections– Propane, acetylene, Mapp gas torch are used for
radiators or larger cable terminal connections
• Stainless steel is not solderable• Flux cleans metal so solder will stick
© 2012 Delmar, Cengage Learning
Soldering (cont'd.)• Cold solder connection
– Solder melts but wire does not bond to it
• Heat-shrink tubing – Insulates a solder joint and makes it airtight
• Connection can also be insulated with vinyl tape
• Adhesive-lined tubing – Recommended to prevent corrosion
© 2012 Delmar, Cengage Learning
Broken or Damaged Ground Straps
• Engine and body: isolated from frame with rubber mounts– Ground straps between engine and chassis
provide path back to battery through frame
• Broken ground strap may cause:– Burned transmission bushing and drive shaft yolk
– Burned emergency brake cables
– Burned carburetor return spring
– Flickering headlights
– Burned front-wheel bearings or CV joints
© 2012 Delmar, Cengage Learning
Circuit Testing and Service• Fuse failure
– Replaced fuse does not fix the problem that caused the overload
• Fix the problem before restoring circuit protection
– Corrosion at fuse end can cause failure
• Fuses are rated according to current capacity– Not voltage
• Fuses have 10% overload factor – Guards against minor power surges
© 2012 Delmar, Cengage Learning
Finding Grounds• Locating the cause of a grounded wire
– Install a circuit breaker temporarily
– Install a test light in series with the circuit breaker
– Disconnect individual circuits
– Circuit disconnected when light goes out is at fault
• Compass or Gauss meter – Locates ground location
• Ohmmeter– Detects grounded circuit
© 2012 Delmar, Cengage Learning
Fuse Testing and Service• Checking fuses
– Visual check, ohmmeter, and test light
• Removing fuses– Blade-type: removed by hand or with pliers
• Test light does not glow on either circuit side – Circuit is shut off
– Circuit is broken
– Tester does not have good ground connection
• Be sure replacement fuse has correct rating
© 2012 Delmar, Cengage Learning
Fuse Link Service• Fuse link
– Length of wire covered with insulation that is thicker than normal insulation
• Can contain melted metal if a wire fails
– Insulation bubbles if fuse link melts• Cut out damaged part of wire• Splice new fuse link• Use a fuse link of the correct size
© 2012 Delmar, Cengage Learning
Headlamp Service• Headlight: light beam from a headlamp• Replacing a headlamp
– Halogen and conventional sealed beams will fit into same brackets
– Round type I and type II lamps do not interchange
– Use dielectric grease when installing headlight
• Halogen lamp replacement– Sealed-beam halogen lamps: replaced as a unit
© 2012 Delmar, Cengage Learning
Headlamp Service (cont’d.)• Composite halogen lamp insert replacement
– Removing a halogen replaceable lamp insert in a composite light assembly
• Touch it only on its plastic base
• HID lamp service– High-intensity discharge (HID) lamps
• Expensive but reliable• Two to three times less likely to fail
© 2012 Delmar, Cengage Learning
Headlight Aiming• Properly aimed low-beams: face down and right• Before adjusting headlights check that the:
– Vehicle is carrying its typical load
– Trunk is carrying typical amount of material
– Gas tank is half-full
– Driver’s weight is accounted for
• Headlight-mounted aimers– Use bubble levels to calibrate vertical alignment
– Horizontal alignment compares headlights to see they are parallel
© 2012 Delmar, Cengage Learning
Headlight Aiming (cont'd.)• Electronic optical aimers
– Laser technology is used to square and align
• Locating the optical center of the headlight– Electronic optical headlight aimer slides on track
• Aimer alignment to headlight– Align the aimer to the headlight
• Lamp audit and aim– Follow arrow indicator
• More precise aiming– Use “Aim Lamp” button
© 2012 Delmar, Cengage Learning
Tail Lamp and Park Light Service
• Lamps may be accessed from inside the trunk– Others require removal of light lens
• Excessive voltage – Shortens the life of a light bulb
• Voltage higher by five percent reduces bulb life by half
– Malfunctioning charging system is the only cause of excessive voltage
© 2012 Delmar, Cengage Learning
LED Service• Light-emitting diodes (LEDs)
– Sometimes used for headlights, brake lights, turn signals, and taillights
– Also used in side rear view mirror turn signal indicators and center high-mount stop lamps
– Not serviceable; they are replaced
– Use less current than filament light bulbs
© 2012 Delmar, Cengage Learning
Stoplight Switch Service• Bypass stoplight switch with jumper wire to test
– Stoplights should light when wires are connected
• Use a test light to see if there is power at one end– If lights come on when wires connected, but not
when brakes are applied, replace the switch
– If lights stoplights operate without key, remove the fuse before removing switch
– If new switch adjustable, adjust it so it is open when the pedal is released
© 2012 Delmar, Cengage Learning
Back-Up Lights• Back-up light circuit components
– Fuse
– Shift lever or transmission mounted switch• Sometimes adjustable
– Wiring
– Lights
• Back-up lights could come on in a gear range other than reverse– Check the service information for adjustment
procedures
© 2012 Delmar, Cengage Learning
Turn Signal Switch• Defective switch
– May not cancel signal following sharp turn
– Brake light problems may be caused by defective signal switch
• Multifunction switch removal– Most newer passenger vehicles use a
multifunction switch • Includes turn signal switch• Can often be removed without removing steering
wheel
© 2012 Delmar, Cengage Learning
Signal Flasher/Relay• Electronic signal flashers
– Flash faster than normal when bulb has failed• Mechanical flashers flash slower
– Turn on hazards and walk around the car to check filaments of signal bulbs and break lights
© 2012 Delmar, Cengage Learning
Locating a Signal Flasher• Several flasher locations
– In the fuse panel
– Under the dash in a wiring loom
– In glove box
– Under the hood
• Location flashers– Most are located under dashboard on driver’s
side
– Working: can be located by clicking sound
– Not working: use service information
© 2012 Delmar, Cengage Learning
Instrument Panel Bulbs and Windshield Washer Service
• Small bulbs resembling photo flash bulbs– Printed circuit dash boards
• Housed in plastic connector• Turn ¼ turn counterclockwise to remove
• Primary reason for windshield washer problems– Restriction in washer nozzle
• Pull one of the hoses off a nozzle and operate washer
• Fluid is pumped from end of hose: clean nozzle• No fluid pumped: check fuse• Problem is with pump: replace it
© 2012 Delmar, Cengage Learning
Horn Service and Gauge Testing
• Horn does not work: check fuse– Horn can adjusted by changing the spring
tension on the armature
• When a gauge does not operate: check its fuse– Fuse in tact, but no power: check wiring diagram
– Work toward battery checking voltage
• Sending unit tests– Use an ohmmeter to check resistance between
the terminal of the sending unit and ground