Rear Window Defogger System Components
The rear window defogger system consist of the following components:
| • | Heating ventilation air conditioning control module |
| • | Body control module (BCM) |
| • | 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 rear defogger relay coil. Battery positive voltage is supplied at all times to the rear defogger relay switched input. When the rear window defogger switch is depressed.
The body control module (BCM) illuminates the rear window defogger indicator in the HVAC control module and sends a ground signal to the BCM. The BCM energizes the rear defogger relay by supplying battery positive voltage through 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 grid.
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.
