GM Service Manual Online
For 1990-2009 cars only

Important: Review the system operation in order to familiarize yourself with the system functions. Refer to the following:

   •  Rear Window Defogger Description and Operation
   •  Automatic Day-Night Mirror Description and Operation

Visual/Physical Inspection

    • Inspect for aftermarket devices which could affect the operation of the rear defogger system. Refer to Checking Aftermarket Accessories in Wiring Systems.
    • Inspect the easily accessible or visible system components for obvious damage or conditions which may cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

    •  Rear Window Defogger Inoperative
    •  Defogger Grid Lines Diagnosis
    •  Automatic Day-Night Mirrors Inoperative
    •  Mirrors - Automatic Day-Night Mirror Displays OC
    •  Mirrors - Automatic Day-Night Mirror Displays SC
    •  Mirrors - Compass/Temperature Display Inoperative or Inaccurate
    •  Mirrors - Temperature Display Inaccurate