Defogger Grid Lines Diagnosis

Defogger Grid Lines Diagnosis

Note:
This test is for reference only. If the rear window defogger element has an open circuit replace the rear window. Refer to Rear Window Replacement Rear Window Replacement.

1. Start the engine.

2. Activate the rear window defogger system.

3. Connect a test lamp to a known ground.





Note:
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 wire to the ground bus wire. The test lamp brilliance may vary from one window to another.

Note:
Care must be taken when probing the rear window defogger with the test lamp probe not to damage the rear window defogger elements.

4. Move the test lamp probe from zone 5 to zone 1 along each grid line.

* 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 Testing for Intermittent Conditions and Poor Connections.





* 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 Rear Window Replacement.