Component Tests and General Diagnostics

Perform before beginning System Diagnosis
1. Check Fuse 3. If open, refer to Chart #2. Chart #2 Rear Defogger Grid and Indicator Inoperative
2. Check Rear Defogger Grid for opens, refer to Body and Frame. Body and Frame
3. Check that grounds G200, G310 and G320 are 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. System Diagnosis - Rear Window Defogger & Heated Mirrors (SSE & SSEI Models)