Heated Mirrors
WARNING: This page is about a different car, the 2003 Buick Regal and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
Battery positive voltage is supplied through the REAR DEFOG circuit breaker in the fuse block to the rear window defogger relay. With the ignition in the ON position, ignition 3 voltage is supplied through the HVAC fuse in the fuse block to the rear window defogger relay coil. When you depress the rear window defogger switch, the rear window defogger indicator illuminates and grounds the control circuit of the rear window defogger relay. This energizes the rear window defogger relay and allows battery positive voltage to the HEATED MIRROR fuse 10A. The HEATED MIRROR fuse provides battery positive voltage to the heated mirrors.