Defogger Grid Lines Diagnosis
- Start the engine.
- Turn the rear window defogger ON.
- Probe each grid line in each zone (1, 2, 3, 4, 5) with a test lamp connected to a good ground.
- If the test lamp does not illuminate anywhere on the grid, the problem may be in the circuit. Refer to Defogger Inoperative - Rear Window .
- 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 Circuit Testing and Wiring Repairs in Wiring Systems.
- If the test lamp goes out, locate the open in that grid line. Test every grid line in at least 2 places (1, 3) to eliminate the possibility of bridging the open (2) in the grid line.
- If an open is located, replace the rear window. Refer to Folding Top Rear Window Replacement in Roof.
IMPORTANT:
The test lamp brilliance will decrease proportionately to the increased resistance in the grid line as the test lamp is moved from the battery positive bus wire to the ground bus wire. The test lamp brilliance may vary from one window to another.