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:

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

Visual/Physical Inspection

    • Inspect for aftermarket devices which could 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 could 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 Indicator Inoperative
    •  Defoggers and Heated Mirrors Always On
    •  Defogger Grid Lines Diagnosis
    •  Automatic Day-Night Mirrors Inoperative
    •  Mirror Compass Display Inoperative or Inaccurate