The rear defogger circuit is protected by a 40A fuse. Voltage is supplied through the fuse to the rear defogger relay. When you press the rear defogger switch, the heater and A/C programer sends a class 2 message to the body control module (BCM), to ground the rear defogger relay coil output circuit. This in turn closes the relay contacts allowing current to the rear window grid.

When you operate the rear defogger switch for the first time, the defog cycle lasts 10 minutes. Further operation results in 5 minute defog cycles. The defog cycle resets to 10 minutes when you turn the ignition switch to the OFF position and back to the RUN position.

The rear defogger feature will not time out if the vehicle speed is above 48 kpa (30 mph).

If the battery voltage is very low, the rear defogger feature is disabled.

The defogger ON indicator is an LED that illuminates when you turn the rear defogger ON.