GM Service Manual Online
For 1990-2009 cars only

Step

Action

Normal Result(s)

Abnormal Result(s)*

1

    â€¢ Start the engine.
    â€¢ Move the blower speed selector switch from OFF to the following positions in the following order:
        1. LOW
        2. MEDIUM 1
        3. MEDIUM 2
        4. HIGH
        5. OFF
    â€¢ The blower motor speed increases as the blower speed selector switch is moved towards the HIGH position.
    â€¢ The blower motor speed decreases as the blower speed selector switch is moved towards the LOW position.

2

    â€¢ Engine idling until operating temperature is reached.
    â€¢ Move the mode control to the heat mode.
    â€¢ Move the temperature control to full heat.
    â€¢ Heated air is delivered to the passenger compartment.
    â€¢ Most of the heated air is delivered through the floor outlets with some air delivered to the windshield and side window outlets.
    â€¢ Heating Insufficient
    â€¢ Heat Excessive (Heater Mode)
    â€¢ Air Delivery Improper
    â€¢ Heat Excessive (Vent Mode)
    â€¢  Noise Diagnosis
    â€¢ High or Low Temperature Control Effort

3

    â€¢ Engine still idling.
    â€¢ Move the mode control to the defrost mode.
    â€¢ Move the temperature control to full heat.
    â€¢ Heated air is delivered to the passenger compartment.
    â€¢ Most of the heated air is delivered to the windshield with some air delivered to the side window outlets.
    â€¢ Defrosting Insufficient
    â€¢ Heat Excessive (Heater Mode)
    â€¢ Air Delivery Improper
    â€¢ Heat Excessive (Vent Mode)
    â€¢  Noise Diagnosis
    â€¢ High or Low Temperature Control Effort

4

    â€¢ Engine still idling.
    â€¢ Move the blower speed selector switch to any position except OFF.
    â€¢ Move the temperature control to the full cold position.
    â€¢ Press the A/C switch to ON.
    â€¢ The blower motor runs.
    â€¢ The condenser fan motor runs.
    â€¢ The A/C compressor clutch engages.
    â€¢ Cold air is delivered to the passenger compartment.
    â€¢ The compressor stops running if the engine coolant temperature exceeds 113°C (235°F).
    â€¢ The compressor and the condenser fan motor stop running if any of the following conditions are met:
      â€¢ The A/C system pressure drops below 193 kPa (28 psi)
      â€¢ The A/C system pressure exceeds 3137 kPa (455 psi)
      â€¢ The evaporator core temperature drops below 0°C (32°F)
    â€¢  Condenser Fan Inoperative
    â€¢  Odor Diagnosis
    â€¢  Noise Diagnosis

5

    â€¢ Press the A/C switch to OFF.
    â€¢ Move the blower speed selector switch to OFF.
    â€¢ The blower motor stops.
    â€¢ The A/C compressor clutch disengages.
    â€¢ The condenser fan motor stops once the engine coolant temperature drops below 113°C (235°F).
    â€¢  Blower Motor Always On
    â€¢  Condenser Fan Always On

* Refer to the appropriate symptom diagnostic table for the applicable abnormal result.