Heated Element: Description and Operation

The Rear Defogger System consists of Defogger Relay, Rear Defogger grid, Heater and A/C Programmer, LH and RH Outside Mirrors, Instrument Panel Cluster and related fuses and wiring.

Instrument Panel Cluster (IPC) And HVAC Programmer (ACP)
When the rear defogger is turned ON, the IPC must confirm that the engine is running. The IPC receives engine status from the PCM, via the UART data line. Once engine running status has been confirmed, the IPC switches ON the defogger-ON LED and commands the ACP to turn ON the defoggers, via the UART data line. When the ACP receives this command, it grounds the Defogger Relay coil, through ACP terminal D5.

Another function of the IPC is the timing cycle function. When the 5 or 10 minute cycle has elapsed, the IPC switches OFF the defogger-ON LED and commands the ACP to turn OFF the defoggers, via the UART data line. When the ACP receives this command, it stops grounding the Defogger Relay coil, through ACP terminal D5.

Defogger Relay and Defogger
When the ACP grounds the Defogger Relay coil, the relay energizes causing the relay contacts to close. Battery voltage from Maxi(R) Fuse 5 is applied to Trunk Compartment Fuse Block Fuses B7 and B9. Trunk Compartment Fuse Block Fuse B7 provides battery voltage for the Outside Mirror Defoggers. Trunk Compartment Fuse Block Fuse B9 provides battery voltage for the Rear Window Defogger Grid. When battery voltage is applied to the heating elements, the elements warm and dissipate any fog or ice.