Lighting and Wiring Service

1
Lighting and Wiring Service

• Chapter 33

2
Objectives

• Diagnose problems in lighting and wiring systems
• Adjust headlamp aim
• Make repairs to automotive wiring, lamps and
  bulbs, and protection devices

3
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

4
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

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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

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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

8
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

9
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

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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

11
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

12
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

13
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

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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

16
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

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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

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Headlamp Service (contd.)

• 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

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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
• Drivers weight is accounted for
• Headlight-mounted aimers
• Use bubble levels to calibrate vertical alignment
• Horizontal alignment compares headlights to see
  they are parallel

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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

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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

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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

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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

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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

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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

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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

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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 drivers side
• Working can be located by clicking sound
• Not working use service information

29
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

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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