Testing Grid Lines - Left Hand Drive

Testing Grid Lines:

To locate inoperative grid lines, turn ignition key to the On position and the rear defog switch On. Attach the black lead of the multi meter (set to the 20 volt scale) to ground. Lightly touch the red lead of the multimeter to each grid line.

Testing Grid Lines:

The multimeter should display battery voltage at the positive side (driver side - SC/SL, passenger side - SW) of each grid line. The voltmeter should gradually display less voltage as the red lead of the multimeter is moved toward the passenger side (SC/SL) or driver side (SW) of the vehicle.

If the reading shows battery voltage as the red lead is moved across the grid lines and then makes a sudden jump down to zero volts (ground) that grid line has an open in it.

Items required for grid repair:
^ GM PN 12345345 (or equivalent) Rear Window Defogger Repair Kit
^ Heat gun - capable of 260°C (500°F)