Electric Rear Defogger

WARNING: This page is about a different car, the 2005 Saturn L300. However, it is still accessible from the selected car via links, so may be relevant.

When the rear defog switch input circuit 292 to the body control module (BCM) is momentarily switched to ground, as when the rear defog switch is pressed, the BCM will respond by grounding circuit 193, the coil of the rear defog relay.

This action energizes the rear defog relay providing power to circuit 293-rear defog heater elements, circuit 683-heated mirror relay coil and circuit 683-rear defog LED. Momentarily switching circuit 292 to ground again will result in the BCM turning the rear defog relay OFF.

The first time in an ignition cycle that the rear defog is activated, the rear defog will remain ON or 15 minutes or until the ignition switch is turned OFF. If the rear defog is activated again during the same ignition cycle, the rear defog will remain ON for 7.5 minutes or until the ignition switch is turned OFF.