1. Start the engine.
2. Turn on the rear window defogger system.
3. Ground one lead of a test lamp.
4. With the other lead of the test lamp, lightly touch each end of each grid line.

Observe for the following conditions:

•	The test lamps lights to full brilliance at both ends of the grid lines.

•	The brilliance of the test lamp decreases proportionately as you move the lead from the left side to the right side.

•	This condition is normal.

•	The test lamp does not light at the right end of the grid.

5. If the test lamp lights to full brilliance at both ends, repair the ground.
6. If the light reading is abnormal, move the test lamp along the grid line from left to right until the test lamp extinguishes.

This indicates a break in the grid line.

Test each grid line within each of the 3 zones delineated by the 2 vertical antenna lines. Contact each grid line 3 mm (0.125 in) on either side of the window centerline.