Heated Glass Element Switch: Description and Operation

The rear window defogger switch is integral to the a/c heater control, which is located in the instrument panel center bezel.

The rear window defogger switch and the rear window defogger switch LED indicator cannot be repaired and, if faulty or damaged, the entire a/c heater control must be replaced. (Refer to HEATING & AIR CONDITIONING/CONTROLS/A/C HEATER CONTROL - REMOVAL).

On Manual Temperature Control systems when the rear window defogger switch push button is depressed, it provides a hard wired signal by momentarily closing the rear window defogger switch sense circuit which is monitored by the BCM. On Automatic Temperature Control (ATC) systems, when the defogger switch is depressed, the ATC head sends a switch status message to the BCM over the Programmable Communications Interface (PCI) data bus network. A Light Emitting Diode (LED) in the push button for the rear window defogger switch illuminates to indicate when the rear window defogger system is turned ON. Each time the BCM rear window defogger timer and logic circuitry sees another request, it toggles a control output to the rear window defogger relay Energizing the rear window defogger relay provides electrical current to the rear window defogger grid and to the LED indicator in the switch, which lights to indicate when the defogger system is turned ON. A dedicated fuse in the junction block protects the rear window defogger relay output circuit to the LED indicator.