Important: This test is for reference only. A grid line fault requires rear window replacement. Refer to Rear Window Replacement.

1. Start the engine.
2. Activate the rear window defogger system.
3. Connect a test lamp to a known ground.




Important: All testing is done on the inside of the rear window and each grid line requires testing individually.

Important: The test lamp brilliance will decrease proportionately to the increased resistance in the grid line as the probe is moved from the battery positive bus (1) wire to the ground bus wire (5). The test lamp brilliance may vary from one window to another.

4. Move the test lamp probe along the grids line from zone (1) to zone (5) the test lamp brilliance should decrease when moved in this direction.

•	If the test lamp shows full brilliance at both ends of the grid lines, inspect for an open or poor connection in the ground circuit of the rear window defogger grid. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.





•	If the test lamp goes out, test the grid line in at least 2 places (1,3) to eliminate the possibility of bridging the open (2) in the grid line.

5. Once the open (2) is located, replace the rear window. Refer to Rear Window Replacement.