Rear Defogger: Testing and Inspection

NOTE:
- Illumination of the defogger switch indicator lamp does not necessary mean that electrical current is reaching the rear glass heating grid lines.
- For circuit descriptions and diagrams of the rear window defogger (EBL) system, refer to WIRING DIAGRAM INFORMATION.

Operation of the electric backlight (EBL) system can be confirmed by the following:
1. Use a DRBIII(R) scan tool and check for diagnostic trouble codes (DTCs) related to the instrument cluster. 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 operation can be checked by feeling the surfaces of the rear window glass or outside heated rear view mirror glass, when equipped. A distinct difference in temperature between the grid lines and the adjacent clear glass or the mirror glass should be detected within three to four minutes of operation.

Rear Window Glass Grid Test - Typical:

3. If a temperature difference is not detected, use a 12-volt DC voltmeter and contact the rear glass heating grid power feed terminal A with the positive lead, and terminal B 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 EBL feed wire and ground wire are connected to the terminals. Confirm that the ground wire has continuity to ground.
- Check the EBL relay located in the power distribution center (PDC) in the engine compartment. Check the fuses in the fuse block located in the passenger 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 instrument panel.
- Rear window defogger relay control circuity in the instrument cluster.
- Rear window defogger grid lines (all grid lines would have to be broken, or the power feed or ground wire disconnected, for the entire heated grid to be inoperative).
4. If the EBL system operation has been verified but the rear window defogger indicator does not illuminate, check the indicator power feed fuse located in the fuse block. If the fuse is Ok, replace the rear window defogger switch.