Circuit/System Description
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The R/DEFOG relay supplies voltage to the outside rearview mirror heater elements based on the current state of the rear window defogger. The replay supplies B+ through the driver/passenger mirror heating element supply voltage circuit when a request is seen.