Grid Wire Test

1. Using a bright lamp inside the vehicle, inspect the wire grid from the outside. A broken grid wire will appear as a brown spot.
2. Run the engine at idle. Set the heated back window switch and light to ON. The indicator light should come on.
3. Working inside the vehicle with a 12-volt DC voltmeter such as Rotunda 73 Digital Multimeter contact the broad red-brown stripes of the back glass window positive lead to batter side and negative lead to ground side. The meter should read 10-13 volts. A lower voltage reading indicates a loose ground wire (pigtail) connection at the ground screw.
4. Contact a good ground point with the negative lead of the meter. The voltage reading should not change.
5. With the negative lead of the meter grounded, touch each grid line of the heated back window glass at its midpoint with the positive lead. A reading of approximately 6 volts indicates that the line is good. A reading of zero volts indicates that the line is broken between the midpoint and the B+ side of the grid line. A reading of 12 volts indicates that the circuit is broken between the midpoint of the grid line and ground.