Rear Defogger: Testing and Inspection
NOTE:- Illumination of the defogger switch indicator lamp does not necessary mean that electrical current is reaching the rear window glass and/or the outside rear view mirror heating grids.
- For circuit descriptions and diagrams of the rear window defogger (EBL) and heated mirror systems, refer to WIRING DIAGRAM INFORMATION.
Operation of the electrical backlight (EBL) and heated mirror systems can be confirmed by the following:
1. Use a scan tool and check for diagnostic trouble codes (DTCs) related to the A/C-heater control. If no DTCs are found, go to Step 2. If any DTCs are found, repair as required, then proceed to Step 2
2. Turn the ignition switch to the On position. Set the rear window defogger switch in the On position. The rear window defogger and heated outside rear view mirror operation can be checked by feeling the glass surfaces of the rear window or outside rear view mirrors. A distinct difference in temperature between the grid lines (1) and the adjacent clear glass (2) or the mirror glass should be detected within three to four minutes of operation.
3. If a rear window glass temperature difference is not detected, use a 12-volt DC voltmeter (4) and contact the rear glass heating grid power feed terminal A (3) with the positive lead, and the ground terminal B (5) with the negative lead. The voltmeter should read battery voltage. If the voltmeter does not read battery voltage, check the following:
- Confirm that the ignition switch is in the On position.
- Make sure that the rear glass heating grid feed wire and ground wire are connected to the terminals. Confirm that the ground wire has continuity to ground.
- Check the EBL relay and fuses located in the integrated power module (IPM) in the engine compartment. The relay and fuses must be tight in their receptacles and all electrical connections must be secure. Refer to the appropriate wiring information for diagnosis and testing of the ISO-standard relay.
When the above steps have been completed and the rear glass heating grid is still inoperative, one or more of the following is faulty:
- Rear window defogger switch in the A/C-heater control.
- Rear window defogger grid lines (all grid lines would have to be broken, or the power feed or the ground wire disconnected, for the entire heating grid to be inoperative).
4. If a heated outside rear view mirror glass temperature difference is not detected, use a 12-volt DC voltmeter (4) and contact the rear view mirror glass heating grid power feed terminal 1 with the positive lead, and the ground terminal 5 with the negative lead. The voltmeter should read battery voltage. If the voltmeter does not read battery voltage, check the following:
- Confirm that the ignition switch is in the On position.
- Make sure that the rear view mirror glass heating grid feed wire and ground wire are fully connected to the terminals. Confirm that the ground wire has continuity to ground.
- Check the heated mirror relay and fuse located in the integrated power module (IPM) in the engine compartment. The relay and fuse must be tight in their receptacles and all electrical connections must be secure. Refer to the appropriate wiring information for diagnosis and testing of the ISO-standard relay.
When the above steps have been completed and the rear view mirror glass heating grid is still inoperative, one or more of the following is faulty:
- Rear window defogger switch in the A/C-heater control.
- Rear view mirror grids (both the left and right mirror grids would have to had to fail or the power feed or the ground wire disconnected, for the both mirror grids to be inoperative).
5. If the operation of the EBL system and/or the heated mirror system has been verified but the defogger LED indicator does not illuminate, replace the A/C-heater control.