Rear Window Defrost

When the rear window defrost switch (part of the FCIM-B (Front Controls Interface Module "B")) is activated, a message is sent to the GWM through the HS-CAN3. From there, the message is sent to the HVAC module through the MS-CAN. When the HVAC module receives the request, it grounds the control circuit to activate the rear window defrost relay (located in the BJB). When the rear window defrost relay is activated, the rear window defrost grid is energized and heats the window glass.