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Air Conditioning Compressor Malfunction



Air Conditioning Compressor Malfunction

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview

Circuit/System Description

When the A/C switch is pressed, the HVAC control assembly grounds the A/C request signal circuit. The body control module (BCM) receives the ground input and sends a GMLAN message to the engine control module (ECM) or powertrain control module (PCM) for an A/C request. This input will request the PCM/ECM to ground the A/C compressor clutch relay control circuit, which will switch the A/C CLUTCH relay. With the relay contacts closed, battery voltage is supplied to the A/C compressor clutch assembly.

Diagnostic Aids

The following conditions must be met in order for the PCM/ECM to turn on the compressor clutch:

* Battery voltage is between 9-16 volts.
* Engine coolant temperature (ECT) is less than 123°C (253°F).
* Engine speed is less than 5300 RPM.
* Engine speed is more than 600 RPM.
* A/C high side pressure is between 2951-310 kPa (428-44 psi).
* Throttle position is 100 percent for 10 seconds.
* Evaporator temperature is greater than 0°C (32°F)
* PCM/ECM does not detect excessive torque load
* PCM/ECM does not detect insufficient idle quality.
* For a compressor does not engage condition check the center instrument panels engine coolant temperature gage refer to Engine Overheating for a possible engine overheat condition. Engine Overheating

Circuit/System Verification

1. Press the A/C request switch. The A/C compressor clutch should engage.
2. Place the mode switch in the defrost position. The A/C compressor clutch should engage.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector C2 pin K ground circuit terminal at the HVAC control assembly.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the ground circuit terminal K and ground.

• If greater than 1.0 ohm, test the ground circuit for an open/high resistance.

3. Install a 3-amp fused jumper wire between the signal circuit terminal C2 pin C and ground. With a scan tool, verify the A/C Request Switch parameter is ON.

• If not On, test the signal circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the BCM.

4. Reconnect the harness connector of the HVAC control assembly. With a scan tool, verify the A/C Request Switch parameter cycles between On and Off with each press of the A/C switch.

• If the parameter does not cycle, test the signal circuit for a short to ground. If the circuit tests normal, test or replace the HVAC control assembly.

5. Remove the A/C compressor clutch relay.
6. Verify that a test lamp illuminates between the relay coil B+ circuit pin G3 and ground.

• If the test lamp does not illuminate, test the B+ circuit pin G3 for a short to ground or an open/high resistance.

7. Verify that a test lamp illuminates between the relay switch B+ circuit pin G1 and ground.

• If the test lamp does not illuminate, test the relay switch B+ circuit pin G1 for an open/high resistance. If the A/C fuse 5 is open, test the relay switch control circuit pin H3 for a short to ground. If all circuits test normal, test or replace the A/C compressor clutch.

8. Disconnect the harness connector at the A/C compressor clutch.
9. Ignition OFF test for less than 1.0 ohm of resistance between the A/C compressor ground circuit pin B and ground.

• If greater than 1.0 ohm, test the ground circuit for an open/high resistance.

10. Connect the harness connector at the A/C compressor clutch.
11. Connect a 10-amp fused jumper wire between the relay switch B+ circuit pin G1 and the relay switch control circuit pin H3. Verify the A/C compressor clutch engages.

• If the A/C compressor clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the A/C compressor.

12. Connect a test lamp between the relay control circuit pin H3 and the relay coil B+ circuit pin G3.
13. Using a scan tool, command the A/C relay output ON and OFF. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp remains ON all the time, test for a short to ground on the control circuit. If the circuit tests normal, replace the PCM/ECM.
• If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If the circuit tests normal, replace the PCM/ECM.

14. If all circuits test normal, test or replace the A/C compressor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

* Compressor Replacement (2.0L (LSJ)) Compressor Replacement (2.2L (L61), 2.4L (LE5))
* Control Module References for BCM, PCM, and ECM replacement, setup and programming.
* Compressor Clutch Assembly Replacement (2.0L (LSJ))
* Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center) Verification Tests
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