CH23 electrical accessories STUDENT VERSION rev

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Chapter 23

Electrical Accessories

Windshield Wiper/Washer Systems

• Permanent magnet wiper circuits

– Are the most common design

– Speed is controlled by the placement of the

brushes on the commutator

– Three brushes are used

– Park switch supplies voltage to motor after the wiper switch is turned off

Windshield Wiper Systems (cont’d)

• Electromagnetic field wiper circuits

– Use two fields that are wired in opposite

directions - the shunt field and the series field – A ground side switch determines the path of current flow and motor speed

– The shunt field reduces motor speed

– In high speed the shunt field ground has

resistance, reducing current flow

Common Wiper Concerns

Cruise Control Systems

• Vacuum Systems

– Was the most common system

– A transducer senses and controls speed

– The servo unit controlled the throttle based on vacuum input from transducer

– Had an electrical and vacuum brake-activated switch to disconnect cruise control

Cruise Control Systems (cont’d)

Sound System Diagnosis

• Test the system outside, not in a building

• Check the vehicle’s ignition system if noise

is heard on the radio

• Verify that all wires are properly shielded

• Check speakers for proper mounting

• Always use the manufacturer’s diagnostic procedures

Power Lock Systems

• Reversible motors

• Power and ground supplied through the switch

• May automatically lock doors when

transmission is shifted from park or at a certain speed

Power Trunk Release

• Perform a switch test.

• Check trunk release fuse first, then switch.

Power Windows

• Master control switch

• Individual control switches

• Individual window drive motors

• Express-down module

• Lock-out or disable switch

Power Window System

• Determine if whole system or part is not working

• Use the system wiring schematic to

determine the proper diagnostic procedure

• Test the circuit breaker for the presence of voltage on both sides

• Use a jumper wire to test the motor

• Use a voltmeter to check the switches

Power Seat Types

• Visually inspect wires and connections

• Test for available voltage at the switch

• Use a continuity chart, if available, to check the switch

• If the switch tests good, test the motors

• Unusual noises can be caused by the

motor, transmission, or cables

Power Seat Circuit

Power Mirror System

• A “joystick” allows control of both mirrors from one switch

• Dual motor drive assemblies are located in each mirror assembly

• Some systems automatically adjust for

parking maneuvers

Rear-Window Defroster and

Heated Mirror Systems

• Rear-window defroster heats surface

– Circuit has a switch, relay, and heating element

– Uses a micro-thin coating within laminate

– Directs generator output to windshield

Other Accessories (cont’d)

• Moon (sun) roof

Security and Anti-Theft Systems

• Pass-Key System

– Uses a special resistance or transponder key

• Keyless Entry System

– May use a keypad mounted on the door or a remote key fob

• Smart Keys

– Can lock/unlock doors, allow engine start

Alarm Systems

• Can be active or passive

• Passive systems switch on automatically

• Active systems are activated with remote, keypad, key, or switch

• If a switch is activated the alarm sounds

• Can prevent the engine from starting