Tahoe 2WD V8-4.8L VIN V (2004)
Heated Glass Element: Description and Operation
Rear Window Defogger
REAR WINDOW DEFOGGER DESCRIPTION AND OPERATION
REAR WINDOW DEFOGGER SYSTEM COMPONENTS
The rear window defogger system consist of the following components:
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Heating Ventilation Air Conditioning control module
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Body control module (BCM)
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DEFOG relay
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Rear window that has a number of grid lines
REAR WINDOW DEFOGGER OPERATION
When you turn the ignition to the ON position, ignition voltage is supplied to the DEFOG relay coil. Battery positive voltage is supplied at all times to
the DEFOG relay switched input. When the rear window defogger switch is depressed, the HVAC control module illuminates the rear window
defogger indicator and sends a class 2 message to the BCM. The BCM energizes the DEFOG relay by grounding the control circuit of the relay. This
allows battery positive voltage from the relay switched input through the switch contacts and out the relay switched output to the rear window
defogger. Ground for the rear window defogger is provided by G306. If the vehicle is equipped with cargo doors, ground for the rear window
defoggers will be provided by G410.
When you turn ON the ignition and press the rear window defogger switch for the first time, the defogger cycle lasts 10 minutes. Further operation
results in 5 minute defogger cycles.
