Theory Of Operation

The Rear Defogger Switch is located in the A/C and Heater Control, which sends Climate Control requests to the HVAC Module. When the Body Control Module (BCM) receives CAN Bus message from the HVAC Module, requesting Rear Window Defogger operation, the BCM will provide a ground signal through the Rear Window Defogger Relay Control circuit to activate the Rear Defrost Relay, located in the Rear Power Distribution Center (PDC) Assembly. When the Rear Defrost Relay is activated, the relay provides battery voltage through the Rear Window Defogger Control Output circuit, to the Rear Window Defogger and through the De-Icer Supply circuit to the Passenger and Driver Exterior Rearview Mirrors and if equipped, the Washer Nozzle Heaters.