HVAC System Malfunction

HVAC System Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Aids

Check the following mechanical fault sources:

* Air distribution box

* Air distribution hoses/air distribution ducts

Reference Information

Schematic Reference

HVAC Schematics HVAC - Automatic

Connector End View Reference

Component Connector End Views Outside Rearview Mirror - Driver

Description and Operation

Automatic HVAC Description and Operation HVAC - Automatic

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Special Tools

J43600 - ACR Air Conditioning Service Center

Circuit/System Verification

Note: Check for bulletins before proceeding.

1. Ignition ON.

2. Verify the scan tool parameters listed below change when pressing the appropriate switch.

* Left Temperature Knob

* Right Temperature Knob

* Air Recirculation Mode Switch

* Floor Mode Switch

* Front Defrost Switch

* Multi-Zone Switch

* A/C Switch

* Rear Defogger Switch

* Enhanced Defrost Switch

• If any parameter does not change
Replace the A26 HVAC controls.

• If all parameters change

3. Verify the scan tool Blower Motor Switch parameter changes when using the switch to move through the commanded blower speeds.

• If the parameter does not change for each speed position
Replace the A26 HVAC controls.

• If the parameter changes for each speed position

4. Verify the blower motor operates properly with the blower motor switch in each speed position.

• If the blower motor does not operate in each speed position
Refer to DTC B0193 HVAC - Automatic.

• If the blower motor operates properly in each speed position

5. Verify all HVAC doors move when pressing the appropriate switch.

* Temperature

* Bi-Level mode

* Recirculation

• If any HVAC door does not move
Refer to DTC B0223, B022A, B0233, B023A, B0408, or B0418 HVAC - Automatic.

• If all HVAC doors move

6. Install the J43600 - ACR Air Conditioning Service Center.

7. Verify the high side pressure reading on the Air Conditioning Service Center is within 10% of the scan tool A/C High Side Pressure Sensor parameter.

• If the reading is not within 10%
Refer to DTC P0532 or P0533 HVAC - Automatic.

• If the reading is within 10%

8. Verify the A/C High Side Pressure Sensor parameter is between 269-2929 kPa (39-425 PSI).

• If the reading is not between 269-2929 kPa (39-425 PSI)
Refer to Air Conditioning (A/C) System Performance Test Initial Inspection and Diagnostic Overview.

• If the reading is between 269-2929 kPa (39-425 PSI)

9. Verify the scan tool A/C Evaporator Temperature Sensor parameter is within 10% of ambient temperature.

• If the parameter is not within 10% of ambient temperature
Refer to DTC B0173, B0178, B0509, B0514 or B3933 B0173.

• If the parameter is within 10% of ambient temperature

10. Engine ON, A/C system ON.

11. Verify cool air flows from the ducts with the temperature control in the coldest position.

• If the air is not cool

1. Verify the compressor clutch is engaged.

• If the compressor clutch is not engaged
Refer to Air Conditioning Compressor Malfunction HVAC - Automatic.

• If the compressor clutch is engaged
Refer to Air Conditioning (A/C) System Performance Test Initial Inspection and Diagnostic Overview.

• If the air is cool

12. Engine OFF, ignition ON.

13. Verify the Sunload parameter changes while covering the B10B ambient light sunload sensor with a shop towel or other suitable item.

• If the Sunload parameter does not change
Refer to DTC B0183 B0183.

• If the Sunload parameter changes

14. Verify the actual inside air temperature, using a thermometer, is less than 3°C (5°F) difference from the scan tool Inside Passenger Compartment Air Temp. Sensor parameter.

• If greater than a 3°C (5°F) difference
Refer to DTC B0163 B0163.

• If less than a 3°C (5°F) difference

15. Verify the scan tool parameters listed below are less than 3°C (5°F) of the actual duct temperature.

* Lower Left Duct Air Temperature Sensor

* Upper Left Duct Air Temperature Sensor

* Lower Right Duct Air Temperature Sensor

* Upper Right Duct Air Temperature Sensor

• If 3°C (5°F) or greater
Refer to DTC B0173, B0178, B0509, B0514 or B3933 B0173.

• If less than 3°C (5°F)

16. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* HVAC Component Replacement Reference Removal and Replacement

* Control Module References Control Module References for HVAC control module replacement, programming, and setup