The rear window defogger system consist of the following components:

Battery positive voltage is supplied through the RR DEFOG fuse in the underhood fuse block to the HVAC control assembly. Ignition voltage is supplied through the HTR/AC fuse in the IP fuse block to the HVAC control assembly. When you turn the ignition to the ON position, and depress the rear window defogger switch. The HVAC control assembly illuminates the rear window defogger indicator and allows battery positive voltage to the rear window defogger grid. Ground for the rear window defogger grid is provided by G106.

When you start the engine and depress the rear window defogger switch, the defogger cycle lasts for 10 minutes. Further operation will result in 10 minute defogger cycles.