Testing Rear Window Defogger Grid Line

If it has been observed during use that a grid line is inoperative, the following procedure can be used to find the break. If none of the grid lines is operating, a full system diagnosis should be completed before attempting to repair the grid lines.

1. Turn the ignition ON.
2. Turn the rear window defogger on.
3. From the inside of the vehicle, connect a voltmeter to each end of a grid line. The voltmeter will indicate battery voltage if the grid line is open.
   CAUTION: Use care when touching the voltmeter leads to a grid line. If the leads are roughly applied, the grid line may be scratched, resulting in an open circuit.
4. If a grid line is found to be open, move a voltmeter lead from one side of the grid line and retest at a point nearer to the other side of the window. Continue to retest, each time bringing one of the voltmeter leads closer to the opposite side of the window from where it was originally placed. The break in the grid line is at the point where the voltmeter begins reading 0 volts instead of battery voltage.
5. Use a marking crayon to lightly mark the break point on the rear window. Mark the glass instead of marking directly on the grid line, and make the mark far enough from the grid line so that it can easily be removed without disturbing the repair.
6. Use a grid line repair kit to fix the break in the grid line. Refer to "REAR WINDOW DEFOGGER GRID LINE REPAIR :".

Outside Rearview Mirror Defoggers