GM Service Manual Online
For 1990-2009 cars only

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

   • If equipped with the C60 system, refer to Control Assembly Description .
   • If equipped with the C34 system, refer to

Visual/Physical Inspection

    • Inspect for aftermarket devices which could affect the operation of the HVAC System. 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:

    •  Blower Motor Inoperative at Any Speed
    •  Blower Motor Operates at High Speed Only
    •  Blower Motor Inoperative in One Speed Only
    •  Blower Motor High Speed Inoperative
    •  Blower Motor Always On
    •  Air Delivery Improper
    •  Temperature Control Inoperative
    •  Defrosting Insufficient
    •  Defrost Air Inoperative
    •  Air Recirculation Inoperative
    •  Cooling Insufficient - Air Conditioning (A/C) System
    •  HVAC Compressor Clutch Does Not Engage
    •  HVAC Compressor Clutch Does Not Disengage
    •  Heating Insufficient
    •  Auxiliary Heating Insufficient
    •  Cold Drafts on Floor
    •  Noise Diagnosis - Air Conditioning (A/C) System
    •  Odor Diagnosis