GM Service Manual Online
For 1990-2009 cars only

Important: The following steps must be completed before using the symptom tables.

  1. Perform the Diagnostic System Check - HVAC Systems - Automatic before using the Symptom Tables in order to verify that all of the following are true:
  2. 1.1. There are no DTCs set.
    1.2. The control module(s) can communicate via the serial data link.
  3. Review the system operation in order to familiarize yourself with the system functions. Refer to
  4. 2.1.  Air Delivery Description and Operation
    2.2.  Air Temperature Description and Operation

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to Checking Aftermarket Accessories in Wiring Systems.
  2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
  3. Verify the A/C compressor clutch turns freely and is not seized.
  4. Verify that the customer is using the correct key to enable personalization and is not inadvertently activating auxiliary HVAC controls.
  5. The A/C compressor will not operate in cold outside air temperatures. Refer to Air Temperature Description and Operation .
  6. The following conditions may cause window fogging:
  7.  - Wet carpet or mats
     - High humidity
     - Interior water leak
     - Blocked A/C evaporator drain tube
     - Maximum passenger capacity
     - Blocked body pressure relief valves
  8. Inspect the air distribution system for causes of reduced air flow:
  9. • 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 in Wiring Systems.

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
    •  Auxiliary Blower Motor Always On
    •  Auxiliary Blower Motor Inoperative
    •  Auxiliary Blower Motor Malfunction
    •  Too Hot in Vehicle
    •  Too Cold in Vehicle
    •  Too Hot in Vehicle - Auxiliary
    •  Too Cold in Vehicle - Auxiliary
    •  Outside Air Temperature Display Inaccurate or Inoperative
    •  Air Delivery Improper
    •  Air Delivery Improper - Auxiliary
    •  Air Recirculation Malfunction
    •  Leak Testing in Heating, Ventilation and Air Conditioning
    •  Defrosting Insufficient in Heating, Ventilation and Air Conditioning
    •  High or Low Temperature Control Effort in Heating, Ventilation and Air Conditioning
    •  Noise Diagnosis - Blower Motor in Heating, Ventilation and Air Conditioning
    •  Noise Diagnosis - Air Conditioning (A/C) System in Heating, Ventilation and Air Conditioning
    •  Odor Diagnosis in Heating, Ventilation and Air Conditioning