Air Conditioning Compressor Malfunction

Air Conditioning Compressor 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 Fault Information






Circuit/System Description

When the A/C switch is pressed, the HVAC control module sends an A/C request message to the engine control module (ECM) via CAN-Bus. Therefore the ECM grounds the A/C compressor clutch relay control circuit, which will switch the A/C compressor clutch relay. With the relay contacts closed, battery voltage is supplied to the A/C compressor clutch. The A/C compressor clutch will be activated.

Diagnostic Aids

The following conditions must be met in order for the HVAC control module to turn on the A/C compressor:

* Battery voltage is between 9-18 V.

* Engine coolant temperature is less than 124°C (255°F).

* Engine speed is greater than 600 RPM.

* Engine speed is less than 5 500 RPM.

* A/C high side pressure is between 269-2 929 kPa (39-425 PSI).

* Throttle position is less than 100%.

* Evaporator temperature is greater than 3°C (38°F).

* ECM does not detect immoderate torque load.

* ECM does not detect insufficient idle quality.

* The ambient temperature is above 1°C (34°F).

Reference Information

Schematic Reference

HVAC Schematics HVAC - Manual

Connector End View Reference

Component Connector End Views Sunshade - Left Front

Description and Operation

Manual HVAC Description and Operation HVAC - Manual

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 Programming and Relearning for scan tool information

Circuit/System Testing

Note:
Before executing Circuit/System Testing, all conditions shown in Diagnostic Aids must be met.

1. Ignition ON, activate and deactivate the A/C switch. Verify the scan tool A/C Switch parameter changes between Active and Inactive.

• If not the specified value, replace the A20 Radio/HVAC Control.

2. Activate and deactivate the A/C switch. Verify the engine control module (ECM) scan tool A/C Request Signal parameter changes between Active and Inactive.

• If not the specified value, replace the K33 HVAC Control Module.

3. Ignition OFF, remove the KR29 A/C Compressor Clutch Relay.

4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

5. Verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.

• If the test lamp illuminates, test the control circuit for a short to voltage.

6. Ignition OFF, disconnect the harness connector at the Q2 A/C Compressor Clutch.

7. Test for less than 5 ohms between the Q2 A/C Compressor Clutch ground circuit terminal A and ground.

• If greater than the specified value, test the ground circuit for an open/high resistance.

8. Connect the harness connector at the Q2 A/C Compressor Clutch.

9. Ignition ON, connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the Q2 A/C Compressor Clutch is activated.

• If the Q2 A/C Compressor Clutch does not activate, test the control circuit for an open/high resistance. If the circuit test normal, replace the Q2 A/C Compressor Clutch.

10. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86.

11. Command the engine control module (ECM) A/C Relay output function ON and OFF with the scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp always illuminates or always does not illuminate, replace the K20 Engine Control Module.

12. If all circuits test normal, replace the KR29 A/C Compressor Clutch Relay.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Air Conditioning Compressor Replacement (LEA) Removal and ReplacementAir Conditioning Compressor Replacement (LFW) Removal and Replacement

* Radio Control Assembly Replacement Radio Control Assembly Replacement

* Control Module References Programming and Relearning for HVAC Control Module replacement, setup, and programming