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 Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
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 Switch
* Right Temperature Switch
* Air Recirculation Mode Switch
* Mode Switch
* Multi-Zone Switch
* A/C Switch
* Rear Defogger Switch
* Enhanced Defrost Switch
• If any parameter does not change
Replace the A20 radio/HVAC controls.
• If all parameters change
3. Verify the scan tool Blower Motor Switch parameter changes when rotating the blower switch through each speed position.
• If the parameter does not change for each speed position
Replace the A20 radio/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 properly in each speed position
Refer to DTC B0193 B0193.
• 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, B0418, B0428, or B3531 B0223.
• If all HVAC doors move
Note: The refrigerant in this vehicle could be either R-134a or R-1234yf. This will determine the correct special tool to use in step 7.
* R-134a - J43600 - ACR Air Conditioning Recharge Service Center
* R-1234yf - GE48800 - ACR Air Conditioning Recharge Service Center
7. Install the appropriate ACR Air Conditioning Recharge Service Center.
8. 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 P0532.
• If the reading is within 10%
9. 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 Air Conditioning (A/C) System Performance Test.
• If the reading is between 269-2929 kPa (39-425 PSI)
10. 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, B0519, B3583, or B3933 B0173.
• If the parameter is within 10% of ambient temperature
11. Engine ON, A/C system ON.
12. Verify cool air flows from the ducts with the temperature control in the coldest position.
• If the air is not cool
Verify the compressor clutch is engaged.
• If the compressor clutch is not engaged
Refer to DTC P0645 P0645.
• If the compressor clutch is engaged
Refer to Air Conditioning (A/C) System Performance Test Air Conditioning (A/C) System Performance Test.
• If the air is cool
13. Verify warm air flows from the ducts with the temperature control in the warmest position.
• If the air is not warm
Refer to Heating Performance Diagnostic Heating Performance Diagnostic.
• If the air is warm
14. Engine OFF, ignition ON.
15. 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 B0163 B0163.
• If the Sunload parameter changes
16. 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 B0183 B0183.
• If less than a 3°C (5°F) difference
17. 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
* Lower Rear Duct Air Temperature Sensor (only with CJ4)
* Upper Rear Duct Air Temperature Sensor (only with CJ4)
• If 3°C (5°F) or greater
Refer to DTC B0173, B0178, B0509, B0514, B0519, B3583, or B3933 B0173.
• If less than 3°C (5°F)
18. 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