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:

   •  Air Delivery Description and Operation
   •  Air Temperature Description and Operation

Visual/Physical Inspection

    • Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to Checking Aftermarket Accessories .
    • Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
    • Verify the A/C compressor clutch turns freely and is not seized.
    • The A/C compressor will not operate in cold outside air temperatures. Refer to Air Temperature Description and Operation .
    • The following conditions may cause window fogging:
       - Wet carpet or mats
       - High humidity
       - Interior water leak
       - Blocked A/C evaporator drain tube
       - Maximum passenger capacity
       - Blocked body pressure relief valves
    • Inspect the air distribution system for causes of reduced air flow:
       - Obstructed or dirty passenger compartment air filter, if equipped
       - Blocked or damaged air inlet or outlet vents

Intermittent

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

Symptom List

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

    •  HVAC Compressor Clutch Does Not Engage
    •  HVAC Compressor Clutch Does Not Disengage
    •  Blower Motor Always On
    •  Blower Motor Inoperative
    •  Blower Motor Malfunction
    •  Too Hot in Vehicle
    •  Too Cold in Vehicle
    •  Air Delivery Improper
    •  Leak Testing
    •  Defrosting Insufficient
    •  Noise Diagnosis - Blower Motor
    •  Noise Diagnosis - Air Conditioning (A/C) System
    •  Noise Diagnosis - HVAC Module
    •  Odor Diagnosis