Rear Window Defogger Grid

DIAGNOSIS AND TESTING - REAR WINDOW DEFOGGER GRID

For complete rear window defogger grid electrical diagnosis with schematics and diagrams, see heated glass electrical diagnostics. Schematics and Diagrams.

To detect breaks in the grid lines, the following procedure is required:

1. Turn the ignition switch to the ON/RUN position. Press the defogger switch to the ON position. The indicator lamp in the defogger switch should light. If OK, go to step 2. If not OK, see heated glass electrical diagnostics.




2. Using a 12-volt DC voltmeter, contact a good body ground point with the negative lead. With the positive lead, contact the vertical bus bar (1) on the left side of the vehicle. The voltmeter should read battery voltage. If OK, go to step 2. If not OK, repair the A/C - Heater Control Module circuit (6) for an open as required.
3. With the negative lead of the voltmeter, contact the vertical bus bar (2) on the right side of the vehicle. The voltage reading should not change. If OK, go to step 3. If not OK, repair the ground circuit (3) for an open as required.
4. Connect the negative lead of the voltmeter to the right side bus bar (2) and touch each grid line (5) at its midpoint (4) with the positive lead. A reading of approximately six volts indicates a line is good. A reading of zero volts indicates a break in the grid line (5) between the midpoint (4) of the grid line and the left side bus bar (1). A reading of ten to fourteen volts indicates a break between the midpoint (4) of the grid line and the right side bus bar (2). Move the positive lead on the grid line (5) towards the break and the voltage reading will change as soon as the break is crossed.