Defogger Grid Lines Diagnosis

Defogger Grid Lines Diagnosis

Note: If it has been observed during use that a grid line is inoperative, the following procedure can be used to find the break. If none of the grid lines is operating, a full system diagnosis should be completed before attempting to test the grid lines

Note: Lightly touch the grid lines when testing with the test lamp. If the test lamp point is scraped through the grid line it can cause an open in the circuit

1. Engine running, command the Rear Defogger ON with a scan tool.

2. Verify that a test lamp illuminates between each rear window defogger grid line and ground. The test lamp should be off when testing at the ground side of the grid and get brighter as the test lamp moves closer to the voltage supply side of the grid. The test lamp should be dim when testing each grid line in the middle

• If the test lamp remains bright at the middle of the grid line.
The grid line is open between the test point and the ground side of the grid.

Replace the rear window

• If the test lamp remains off at the middle of the grid line.
The grid line is open between the test point and the voltage supply side of the grid.

Replace the rear window

• If the test lamp remains dim at the middle of each grid line.

3. All OK