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Chevrolet Silverado / GMC Sierra. Service manual - part 3002
or CLOSED position the OPEN or CLOSED relay coil will be supplied accessory voltage and
energized through the appropriate relay control circuit. While the OPEN and CLOSE relays are
in a de-energized state both motor control circuits will be closed to ground. When one of the
relays is energized its motor control circuit will be closed to the battery voltage supply circuit
and the other motor control circuit will remain grounded through the de-energized relay.
REAR WINDOW DEFOGGER DESCRIPTION AND OPERATION
Rear Window Defogger System Components
The rear window defogger system consist of the following components:
HVAC control module
REAR DEFOG relay
Rear window defogger grid
Rear Window Defogger Operation
When the rear defogger switch is pressed, the HVAC control module will illuminate the rear
window defogger indicator and will supply voltage to the defog relay coil. Battery positive
voltage is supplied at all times to the defog relay switched input and the defog relay coil is always
grounded. This allows battery positive voltage from the relay switch contacts to the rear window
defogger grid. The HVAC module also sends a request to the driver door module and passenger
door module to activate the heated mirrors, if equipped.
When the rear window defogger is initially activated, the defogger cycle will last 10 minutes,
further requests will result in 5 minute defogger cycles.
SPECIAL TOOLS AND EQUIPMENT
SPECIAL TOOLS
Illustration
Tool Number/ Description
J-9886-01
Door Handle Clip Remover
2008 Chevrolet Silverado 1500
2008 ACCESSORIES & EQUIPMENT Fixed and Moveable Windows - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado