Rear Window Defogger System Components
The rear window defogger system consist of the following components:
| • | A heater and A/C control module |
| • | A body control module (BCM) |
| • | A REAR DEFOG relay |
| • | A rear window that has a number of grid lines |
| • | Two bus bars that are attached to the inside surface of the rear window. |
The battery voltage terminal and ground terminal are soldier to the bus bars.
Rear Window Defogger Operation
Battery positive voltage is supplied to the REAR DEFOG relay switch. With the engine running, the BCM supplies battery positive voltage to REAR DEFOG relay coil. When you depress the rear window defogger switch, the heater and A/C control module illuminates the rear window defogger indicator and grounds the control circuit of the REAR DEFOG relay. This energizes the REAR DEFOG relay and allows battery positive voltage through the REAR DEFOG circuit breaker to the rear window defogger grid. Ground for the rear window defogger is provided by G309.
When you start the engine and press the rear window defogger switch for the first time, the defogger cycle lasts for 15 minutes. Further operation results in 7.5 minute defogger cycles. The defogger cycle resets to 15 minutes when you cycle the ignition to the OFF position and then back to the ON position.
If battery voltage is low, the BCM will be disable the rear window defogger by removing the battery positive voltage supplied to the REAR DEFOG relay coil.
