Heated Glass Element: Testing and Inspection

ELECTRIC BACKLIGHT (EBL) SYSTEM

NOTE: Illumination of the defogger switch indicator lamp does not necessarily mean that electrical current is reaching the rear window glass and/or the outside rear view mirror heating grids.

NOTE: 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. Turn the ignition switch to the Run position. Set the rear window defogger switch in the On position. Rear window defogger operation can be checked by feeling the rear window glass or the outside rear view mirror glass, when equipped with heated outside rear view mirrors. A distinct difference in temperature between the grid lines and the adjacent clear glass or the heated mirror glass should be detected within three to four minutes of operation.

2. If a rear window glass temperature difference is not detected, use a 12-volt DC voltmeter and contact the rear glass heating grid terminal B with the negative lead, and terminal A with the positive lead (Figure 1). The voltmeter should read battery voltage. If the voltmeter does not read battery voltage, check the following:

- Confirm the ignition switch is in the Run position.
- Confirm the rear window defogger switch is in the On position.
- Check that fuse 13 (40 amp) and PTC 4 (8 amp) in the integrated power module (IPM) are OK. The fuse and PTC must be tight in their receptacle and all electrical connections must be secure.
- Confirm the EBL feed wire is connected to the heating grid positive terminal and that there is continuity between the window defogger (EBL) relay and the heating grid.
- Confirm the EBL ground wire is connected to the heating grid negative terminal and that there is continuity to ground.
3. When the above steps have been completed and the glass heating grid is still inoperative, one or more of the following is faulty. It may be necessary to connect a DRBIII(R) scan tool to perform further diagnostics. Refer to Body Diagnostic Procedures.

- Rear window defogger switch in the A/C-heater control.
- J1850 bus communication between the A/C-heater control and the front control module (FCM).
- Rear window defogger (EBL) relay in the IPM.
- Rear window defogger control circuity in the FCM.
- Side view mirror heating grid (when only one side view mirror is inoperative).
4. If broken defogger grid lines or bus bars are suspected, use a 12-volt DC voltmeter and contact the rear glass heating grid ground terminal B with the negative lead and each rear glass heating grid line at its mid-point C with the positive lead. The voltmeter should read approximately 6 volts at each grid line mid-point. If the voltmeter does not read approximately 6 volts, repair the open grid line(s) or bus bar(s).

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.






Figure 1 Grid Line Test