Heated Glass

DIAGNOSIS AND TESTING - REAR WINDOW DEFOGGER SYSTEM

For complete heated glass electrical diagnosis with schematics and diagrams, see the appropriate Heated Glass Electrical Diagnostics. For complete heated mirror electrical diagnosis with schematics and diagrams, see the appropriate Heated Mirror Electrical Diagnostics.

The operation of the Electrically Heated Rear Window Defogger System can be confirmed in the following manner:

- Turn the ignition switch to the ON/RUN position.
- Press the Defogger Switch to the ON position. The rear window defogger operation can be checked by feeling the rear window glass and the side view mirrors. A distinct difference in temperature between the grid lines and the adjacent clear glass can be detected within three to four minutes of operation.
- Using a 12-volt DC voltmeter, contact the rear glass heating grid terminal (right side) with the negative lead and the opposite terminal (left side) with the positive lead. The voltmeter should read battery voltage.

The above checks will confirm system operation. Illumination of the Defogger Switch indicator lamp indicates that there is electrical current available at the A/C Heater Control Module but does not confirm that the electrical current is reaching the rear glass heating grid lines and the side view mirrors.

If the defogger system does not operate, the problem should be isolated in the following manner:

1. Confirm that the ignition switch is in the ON/RUN position.

2. Ensure that the rear glass heating grid power feed, and ground wires are connected to the glass.

3. Confirm that the ground wire has continuity to ground.

4. Ensure that each of the power mirrors are fully functional.

5. Check Fuses 4, 25 and 26 in the Underhood Accessory Fuse Block. The fuses must be tight in their receptacles and all electrical connections must be clean and secure.

When the above steps have been completed and the rear glass heating grid/heated mirrors are still inoperative, one or more of the following is faulty:

- Defogger Switch
- A/C Heater Control Module circuitry
- Rear window grid lines (all grid lines would have to be broken or one of the feed wires disconnected for the entire system to be inoperative)