Window Defogger Grid Lines Test

For circuit descriptions and diagrams, refer to Rear Window Defogger in Wiring Diagrams. To detect breaks in the grid lines, the following procedure is required:
1. Turn the ignition switch to the ON position. Set the defogger switch in the ON position. The indicator lamp should light. If OK, go to Step 2. If not OK, (Refer to ELECTRICAL/HEATED GLASS/REAR WINDOW DEFOGGER SWITCH - DIAGNOSIS AND TESTING).
2. Using a 12-volt DC voltmeter, contact the vertical bus bar on the right side of the vehicle with the negative lead. With the positive lead, contact the vertical bus bar on the left side of the vehicle. The voltmeter should read battery voltage. If OK, go to Step 3. If not OK, repair the open circuit to the defogger relay as required.
3. With the negative lead of the voltmeter, contact a good body ground point. The voltage reading should not change. If OK, go to Step 4. If not OK, repair the circuit to ground as required.
4. Connect the negative lead of the voltmeter to the right side bus bar and touch each grid line at midpoint C with the positive lead. A reading of approximately 6 volts indicates a line is good. A reading of 0 volts indicates a break in the grid line between midpoint C and the left side bus bar. A reading of 10 - 14 volts indicates a break between midpoint C and the right side bus bar. Move the positive lead on the grid line towards the break and the voltage reading will change as soon as the break is crossed.