GM Service Manual Online
For 1990-2009 cars only

Object Number: 280276  Size: MF

Perform the following test using the control assembly in order to determine whether the following are working properly:

    • The electrical system
    • The vacuum system
    • The refrigeration system
  1. Check the blower speed from the LOW to the HIGH range in order to verify the proper operation of the following components:
  2. • The blower switch
    • The blower motor
    • The blower resistor
    • The high blower relay
  3. Test each mode to verify the proper function of the following systems:
  4. • Proper air flow distribution
    • Correct function of the vacuum connections and their associated parts
    • Correct function of the complete electrical system, including the following:
       • The electrical actuators
       • The temperature sensors
       • The electrical connections and associated parts
  5. Verify that each of the modes responds as follows:
  6. 3.1. The Max A/C Mode:
       • Air flow from the A/C outlets, including the lap air outlets
       • The recirculation door closes
       • The blower motor sounds louder than in the Normal A/C mode
       • The A/C compressor operates
    3.2. The Normal A/C Mode:
       • Air flow from the A/C outlets, including the lap air outlets
       • The recirculation door opens
       • The A/C compressor operates
    3.3. The Bi-Level A/C Mode:
       • Air flow from the A/C outlets, including the lap air and heater outlets
       • The A/C compressor operates
    3.4. The Vent Mode:
       • Air flow from the A/C outlets, including the lap air outlets
       • The A/C compressor does not operate
       • Small amount of air will come out from the heater outlet
    3.5. The Heater Mode:
       • Air flow from the heater outlets
       • A small amount of air flow from the defroster outlet and the side window defoggers
    3.6. The Blend Mode:
       • Air flow from the defroster outlet
       • Air flow from the side window defoggers and the heater outlet.
       • The A/C compressor does not operate
    3.7. The Defrost Mode:
       • Air flow from the defroster outlet
       • Air flow from the side window defoggers
       • A small amount of air flow from the heater outlets.
       • The A/C compressor may operate
  7. Test the temperature control selector functions as follows:
  8. 4.1. Check the temperature control knob effort by moving the knob from the BLUE (cold) zone, to the RED (hot) zone.
    4.2. Listen for the valve seating in the full BLUE (cold) zone and the full RED (hot) zone.
    4.3. Check for heated air by placing the temperature control knob in the full RED (hot) zone and the mode knob in the Heater position.
    4.4. Check for cooled air by placing the temperature control knob in the full BLUE (cold) position and the mode knob in the MAX A/C or the NORM A/C positions.

    Note the temperature of the air from the outlets. After one minute of operation, the air from the A/C outlets should be at least -7°C (20°F) below the ambient air temperature.

Checking the temperature range verifies the proper function of the following:

    • All vacuum, electrical, and refrigerant system connections
    • All heater system connections
    • The temperature door in the heater assembly
    • The temperature control knob for temperature selection