Component Tests and General Diagnostics

1. Check IGN Fuse. If open, check CKT 141 for a short to ground.
2. Check Rear Defog Circuit Breaker. If open, check CKT 540 for a short to ground.
3. Check Rear Window Defogger Grid for opens.
4. Check that G400 is clean and tight.
^ Check for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a continuity/voltage check with a system disconnected. These circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a voltage drop with the system operational (under load).
^ Check for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (refer to General Troubleshooting Procedures). Diagnostic Aids
^ Refer to System Diagnosis.