Rear Window Defogger Operation

WARNING: This page is about a different car, the 2004 Pontiac Sunfire and 2004 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

Battery positive voltage is supplied through the RR DEFOG fuse in the IP fuse block to the HVAC control assembly. Ignition voltage is supplied through the HVAC fuse in the IP fuse block to the HVAC control assembly. When the ignition is turned to the ON position, and the rear window defogger switch is depressed, the HVAC control assembly illuminates the rear window defogger indicator and supplies battery positive voltage to the rear window defogger. Ground for the rear window defogger is provided by G302. Ground for the HVAC control assembly is provided by G204.

When the engine is started and the rear window defogger switch is depressed for the first time, the defogger cycle lasts for 10 minutes. Further operation results in 5 minute defogger cycles. The defogger cycle resets to 10 minutes when the ignition is cycled to the OFF position and then back to the ON position.