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 procedures:

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

Visual/Physical Inspection

    • Inspect for aftermarket devices which may affect the operation. 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 Always On
    •  Rear Window Defogger Inoperative
    •  Defogger Indicator Inoperative
    •  Defogger Grid Lines Diagnosis
    •  Automatic Day-Night Mirrors Inoperative