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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Corvette 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 HVAC System Check

HVAC System Check CJ2


Object Number: 191673 Size: SF

HVAC System Check (CJ2)

Step

Action

Normal Result(s)

Abnormal Result(s)*

1
  1. Install the scan tool.
  2. Turn the ignition switch to the ON position.
  3. Select display DTC function with the scan tool.
  4. Check for any stored HVAC, PCM or BCM DTCs related to HVAC operation.

No DTCs are stored in memory or current status.
    • DTC is stored in memory or current status (refer to appropriate DTC table).
    • Scan Tool Does Not Communicate with Component.

2
  1. Turn ignition to the OFF position.
  2. Remove the scan tool from the diagnostic link connector.
  3. Start the engine and allow the vehicle to idle in Park until the engine reaches operating temperature.
  4. Close the vehicle doors and windows.
  5. Engine decklid in the closed position.
  6. Press the HVAC mode control button until the UPPER air delivery position is reached.
  7. Turn the blower switch to position four.
  8. Turn the driver's side temperature control knob to the 32°C (90°F) position.
  9. Press the A/C button so that it is in the OFF position.
  10. Press the OUTSIDE AIR button to the ON position.
  11. Install an accurate thermometer into the UPPER air outlet.
  1. Air flows from the instrument panel outlets.
  2. A/C is disengaged.
  3. Hot air is delivered to passenger compartment.
  4. Blower fan operates at medium speed.
  5. Delivered air temperature is approximately between 63°C and 68°C (145°F and 155°F) measured in typical garage settings (21°C to 24°C (70°F to 75°F)).
    • HVAC Compressor Clutch Does Not Disengage.
    • Blower Motor Inoperative At Any Speed.
    • Air Temperature Control Inoperative (CJ2).
    • Air Temperature Control Inoperative--Passenger (CJ2).
    • Air Delivery Improper (CJ2).
    • Heating Insufficient.
    • Noise Diagnosis (Blower Motor).
    • Blower Has High Speed Only.

3
  1. Doors and windows still closed.
  2. Engine decklid in the closed position.
  3. Depress the A/C button to the ON position.
  4. Depress the AUTO button.
  5. Turn the driver's side temperature control knob to the maximum cold position.
  6. Thermometer still installed in the UPPER air outlet.
  1. Air flows from the instrument panel outlets.
  2. A/C light illuminates and compressor is engaged.
  3. Cold air is delivered to passenger compartment.
  4. Blower fan operates at maximum speed.
  5. Delivered air temperature is approximately 18°C (30°F) lower than ambient air temperature.
  6. Air delivery may switch between RECIRC and OUTSIDE AIR position.
    • Noise Diagnosis (Blower Motor).
    • Noise Diagnosis (A/C System)
    • Cooling Insufficient, A/C System.
    • Blower Motor Inoperative At Any Speed.
    • Air Delivery Improper (CJ2).
    • Air Temperature Control Inoperative (CJ2).
    • Air Temperature Control Inoperative--Passenger (CJ2).
    • HVAC Compressor Clutch Does Not Engage.
    • Blower Has High Speed Only.

4

Depress the fan control button until the fan reaches low speed.
    • Blower speed decreases as long as fan control button is depressed.
    • Blower speed is displayed.
    • Blower runs at speed attained when fan control button is released.
    • Blower Motor Inoperative At Any Speed.
    • Noise Diagnosis (Blower Motor).
    • Blower Has High Speed Only.

5

Depress the fan control button until the fan reaches high speed.
    • Blower speed increases as long as fan control button is depressed.
    • Blower speed is displayed.
    • Blower runs at speed attained when fan control button is released.
    • Blower Motor Inoperative At Any Speed.
    • Noise Diagnosis (Blower Motor).
    • Blower Has High Speed Only.

6

Rotate the driver's side temperature control knob until the temperature display reaches 22°C (73°F).
    • Driver's set temperature display drops one degree at a time (stops at 22°C (73°F)).
    • Blower speed reduces as in-car temperature approaches 22°C (73°F).
    • A/C system maintains in-car temperature at approximately 22°C (73°F).
    • Air delivery may switch between the UPPER, BILEVEL, DEFOG and LOWER position depending on ambient conditions.
    • Air delivery may switch between RECIRC and OUTSIDE AIR position depending on ambient conditions.
    • Air Delivery Improper (CJ2).
    • Air Temperature Control Inoperative (CJ2).
    • Air Temperature Control Inoperative--Passenger (CJ2).
    • Noise Diagnosis (Blower Motor).
    • Noise Diagnosis (A/C System).

7
  1. Allow the car to idle for 5-10 minutes in the AUTO setting with the temperature at 22°C (73°F).
  2. Rotate the passenger's side temperature control knob to the maximum heat position.
  3. Rotate the passenger's side temperature control knob to the maximum cold position.
  4. Return the passenger's side temperature control knob to the neutral position.
    • Passenger's side air flow becomes warmer then the master setting.
    • Passenger's side air flow becomes cooler then the master setting.
    • Passenger's side air flow returns to the master setting.
    • Air Temperature Control Inoperative--Passenger (CJ2).
    • Noise Diagnosis (Blower Motor).
    • Noise Diagnosis (A/C System).

8
  1. Depress the mode control button until the instrument panel UPPER position is displayed.
  2. Rotate the driver's side temperature control knob until the temperature display reaches 15°C (60°F).
  3. Push the A/C button to the OFF position.
  4. Depress the OUTSIDE AIR control button.
    • Air flows from the panel outlets.
    • A/C is disengaged.
    • Outside (ambient temperature) air is delivered to passenger compartment
    • Air Delivery Improper (CJ2).
    • HVAC Compressor Clutch Does Not Disengage.
    • Noise Diagnosis (Blower Motor).

9

Depress the mode control button until the LOWER floor position is displayed.
    • Air flows from the floor outlets.
    • A/C is disengaged.
    • Air Delivery Improper (CJ2).
    • HVAC Compressor Clutch Does Not Disengage.
    • Noise Diagnosis (Blower Motor).

10

Depress the mode control button until the DEFOG position is displayed.
    • Air flows from the floor and windshield outlets.
    • A/C compressor is engaged with ambient temperature greater than 2°C (35°F).
    • Air Delivery Improper (CJ2).
    • HVAC Compressor Clutch Does Not Engage.
    • Noise Diagnosis (Blower Motor).
    • Noise Diagnosis (A/C System).

11

Depress the mode control button until the BILEVEL position is displayed.
    • Air flows from the instrument panel and floor outlets.
    • A/C is disengaged.
    • Air Delivery Improper (CJ2).
    • HVAC Compressor Clutch Does Not Disengage.
    • Noise Diagnosis (Blower Motor).

12

Depress the front window DEFROSTER button.
    • Air flows from the windshield outlets.
    • A/C is engaged with ambient temperature greater than 2°C (35°F).
    • Air Delivery Improper (CJ2).
    • HVAC Compressor Clutch Does Not Engage.
    • Noise Diagnosis (Blower Motor).
    • Noise Diagnosis (A/C System).

13
  1. Depress the mode control button until the UPPER position is displayed.
  2. Depress the A/C button to the ON position.
  3. Rotate the driver's side temperature control knob until the temperature display reaches 15°C (60°F).
  4. Depress the RECIRC control button.
    • Air flows from the instrument panel outlets.
    • A/C is engaged.
    • Air recirculates within the vehicle.
    • Fan speed increases.
    • Air Delivery Improper (CJ2).
    • HVAC Compressor Clutch Does Not Engage.
    • Noise Diagnosis (Blower Motor).
    • Noise Diagnosis (A/C System).

14
  1. Depress the A/C button to the OFF position.
  2. Depress the OUTSIDE AIR control button.
    • Air flows from the instrument panel outlets.
    • A/C is disengaged.
    • Outside air circulates into the vehicle.
    • Fan speed decreases.
    • Air Delivery Improper (CJ2).
    • HVAC Compressor Clutch Does Not Disengage.
    • Noise Diagnosis (Blower Motor).

15

Depress the OFF button.
    • HVAC system shuts OFF.
    • Outside air temperature is displayed on the HVAC control panel after a five second display of driver's set temperature.
    • Blower Motor Always On.
    • DTC B0332 Outside Air Temp Sensor Short to GND.
    • DTC B0333 Outside Air Temperature Sensor Open.
    • Blower Has High Speed Only.

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