Heated Glass Element Switch: Description and Operation

REAR WINDOW DEFOGGER SWITCH
The rear window defogger switch is installed in the instrument panel HVAC control head assembly. The momentary-type switch provides a hard-wired ground signal to the HVAC control head each time it is depressed. The instrument cluster rear window defogger timer and logic circuitry responds by energizing or de-energizing the rear window defogger relay.

Energizing the rear window defogger relay provides electrical current to the rear window defogger grid and, if the vehicle is so equipped, the outside rear view mirror heating grids. An amber indicator lamp in the defogger switch, which lights to indicate when the defogger system is turned ON, is also powered by the defogger relay output.

The defogger switch illumination lamp and indicator lamp bulbs are serviceable. The defogger switch cannot be repaired and, if faulty or damaged the entire HVAC control head assembly must be replaced.