HVAC Control Module

Rear Defog Output:  The scan tool displays On/Off. When the rear window defogger switch is depressed, the HVAC control module energizes the Rear Window Defogger relay by grounding the control circuit of the relay, which the scan tool displays as On.

Rear Defrost Button:  The scan tool displays On/Off. When the rear window defogger switch is depressed, the scan tool will momentarily display On.