GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Firebird 🢒 Body and Accessories 🢒 Wiring Systems 🢒 Functional Check

This operational test sequence aids in determining whether the following systems are working properly:

    • Air conditioning (A/C)
    • Air conditioning (A/C) electrical
    • Vacuum
    • Refrigeration
  1. Ensure that the temperature of the air is at least 16°C (60°F). The A/C system can not be properly tested unless it is at least this warm.
  2. Start the engine.
  3. Allow the engine to idle the engine for 20 minutes or until the cooling system thermostat is open.
  4. Perform the Functional Check.
  5. Compare the vehicle response to the normal system response.
  6. If the vehicle does not respond correctly to any of the steps, use one of the following procedures in order to begin the appropriate diagnosis:
    7. • Insufficient heating
    • Refer to Heating Insufficient
    • Insufficient cooling
    • Refer to Cooling Insufficient - Air Conditioning (A/C) Inoperative
    • Improper air delivery
    • Refer to Air Delivery Improper
    • Blower motor inoperative. Refer to Blower Motor Inoperative at Any Speed

Functional Check

Step

Action

Normal Result(s)

Abnormal Result(s)*

1
  1. Place the mode control knob in the OFF position.
  2. Place the temperature control knob in the COLD (blue) position.
  3. Place the blower motor knob in the LOW fan position.
    • The blower motor speed is OFF.
    • There is no airflow from the heater outlets.
    • There is no airflow from the A/C outlets.
    • There is no air flow from the defroster outlets.
    • Airflow from the heater, A/C, or defroster outlets.
    • Apply vacuum to each vacuum line individually (except black and orange)
    • If air flows out the outlets repair or replace the actuator linkage and/or air valve (door).
    • Blower motor runs.

2
  1. Place the mode control knob in the MAX A/C setting.
  2. Place the temperature control knob in the COLD setting.
  3. Place the blower motor knob in the LOW setting.
    • The blower motor speed is LOW.
    • There is no airflow from the heater outlets.
    • There is airflow from the A/C outlets.
    • There is no air flow from the defroster outlets.
    •  Temperature from the center A/C outlet should drop 11°C (20°F) from the temperature outside the vehicle.
    • Engagement of the detent is felt in each mode.
    • Airflow from the heater or defroster outlets. No airflow from the A/C outlets.
    • Temperature does not change.
    • No blower motor speed change.
    • Blower motor speed inop.

3
  1. Place the mode control knob in the MAX A/C setting.
  2. Place the temperature control knob in the COLD setting.
  3. Place the blower motor knob in the LOW to HIGH setting.
    • The blower motor speed is LOW to HIGH.
    • There is no airflow from the heater outlets.
    • There is airflow from the A/C outlets.
    • There is no air flow from the defroster outlets.
    • Temperature from the center A/C outlet should drop 11°C (20°F) from the temperature outside the vehicle.
    • A noticeable blower speed increase occurs from the following settings:
      • LOW
      • MEDIUM LOW
      • MEDIUM HIGH
      • HIGH
    •  The outlets hold their position during high blower motor speed and are moveable by hand.
    • There is airflow from the heater and/or defroster outlets.
    • There is no airflow from the A/C outlets.
    • Temperature does not change.
    • No blower motor speed change.
    • Blower motor speed inop.

4
  1. Place the mode control knob in the NORMAL A/C setting.
  2. Place the temperature control knob in the COLD setting.
  3. Place the blower motor knob in the HIGH setting.
    • The blower motor speed is HIGH.
    • There is no airflow from the heater outlets.
    • There is airflow from the A/C outlets.
    • There is no air flow from the defroster outlets.
    • Listen for a reduction of air noise due to the recirculation door closing.
    • Engagement of the detent is felt in each mode control setting.
    • There is airflow from the heater and/or defroster outlets.
    • There is no airflow from the A/C outlets.
    • Temperature does not change.
    • No blower motor speed change.

5
  1. Place the mode control knob in the BI-LEVEL A/C setting.
  2. Place the temperature control knob in the COLD setting.
  3. Place the blower motor knob in the HIGH setting.
    • The blower motor speed is HIGH.
    • There is airflow from the heater outlets.
    • There is airflow from the A/C outlets.
    • There is minimum air flow from the defroster outlets.
    • Engagement of the detent is felt in each mode control setting.
    • Blower motor speed inop.
    • Airflow from the heater outlets.
    • No airflow from the A/C outlets.
    • No engagement of the detent is felt.

6
  1. Place the mode control knob in the VENT setting.
  2. Place the temperature control knob in the COLD setting.
  3. Place the blower motor knob in the HIGH setting.
    • The blower motor speed is HIGH.
    • There is no airflow from the heater outlets.
    • There is airflow from the A/C outlets.
    • There is no air flow from the defroster outlets.
    • Engagement of the detent is felt in each mode control lever setting.
    • Blower motor speed inop.
    • Airflow from the heater and/or defroster outlets.
    • No airflow from the A/C outlets.
    • No engagement of the detent is felt.

7
  1. Place the mode control knob in the HEATER setting.
  2. Place the temperature control knob in the HOT setting.
  3. Place the blower motor knob in the HIGH setting.
    • The blower motor speed is HIGH.
    • There is airflow from the heater outlets.
    • There is no airflow from the A/C outlets.
    • There is minimum air flow from the defroster outlets.
    • Engagement of the detent is felt in each mode control lever setting.
    • The temperature lever travels from full COLD to full HOT.
    • Air flow is present at the side window defogger outlets.
    • Blower motor speed inop.
    • Airflow from the heater, defroster and A/C outlets.
    • No engagement of the detent is felt.

8
  1. Place the mode control knob in the DEFROSTER BLEND setting.
  2. Place the temperature control knob in the HOT setting.
  3. Place the blower motor knob in the HIGH setting.
    • The blower motor speed is HIGH.
    • There is airflow from the heater outlets.
    • There is no airflow from the A/C outlets.
    • There is air flow from the defroster outlets.
    • Engagement of the detent is felt in each mode control lever setting.
    • Air flow is present at the side window defogger outlets.
    • Blower motor speed inop.
    • No airflow from the heater and/or defroster outlets.
    • Airflow from the A/C outlets.
    • No engagement of the detent is felt.
    • No airflow at the side window defogger outlets.

9
  1. Place the mode control knob in the DEFROST setting.
  2. Place the temperature control knob in the HOT setting.
  3. Place the blower motor knob in the HIGH setting.
    • The blower motor speed is HIGH.
    • There is minimum airflow from the heater outlets.
    • There is no airflow from the A/C outlets.
    • There is air flow from the defroster outlets.
    • Engagement of the detent is felt in each mode control lever setting.
    • Air flow is present at the side window defogger outlets.
    • Blower motor speed inop.
    • Airflow from the A/C outlets.
    • No airflow from the defroster outlets.
    • No engagement of the detent is felt.
    • No airflow at the side window defogger outlets.

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