Component Tests and General Diagnostics

DEFOGGER GRID LINES DIAGNOSIS
1. Start the engine.
2. Activate the rear window defogger system.
3. Connect a test lamp to a good ground.





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

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

- 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.





- 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. If an open (2) is located, the rear window must be replaced.

DETECTING MICROCRACKS
1. Start the engine.

IMPORTANT: Only use this procedure for rear window defogger systems that have the radio antenna made on the rear glass or where the rear window defogger is being used as a radio antenna.

2. Turn the radio to a good AM radio station.
3. Activate the rear window defogger system.
4. If crackling noise is heard on the station when the rear window defogger is activated, replace the rear window.