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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 and system conditions are such that A/C operation is allowed, the ECM will ground the A/C compressor clutch relay control circuit, which will switch the KR29 A/C COMPRESSOR CLUTCH relay on. With the relay contacts closed, battery voltage is supplied to the A/C compressor clutch assembly, engaging the A/C compressor.

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

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

Circuit/System Verification

1. Ignition ON.

2. Verify the scan tool A/C Switch parameter changes between Active and Inactive when cycling the A/C switch.

• If the parameter does not change
Replace the K33 HVAC control module.

• If the parameter changes

3. Verify the A/C Compressor Clutch Relay clicks when commanding the A/C clutch ON and OFF with a scan tool.

• If the relay does not click
Refer to Circuit/System Testing

• If the relay clicks

4. All OK.

Circuit/System Testing

1. Ignition OFF, disconnect the KR29 A/C compressor clutch relay, ignition ON.

2. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF.

2. Test for less than 2 ohms in the B+ circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF.

2. Test for infinite resistance between the B+ circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance,

3. Disconnect the harness connector at the Q2 A/C compressor clutch.

4. Test for greater than 1 ohms between the control circuit terminal 87 and ground.

• If less than 1 ohms, repair the short to ground on the circuit.

• If greater than 1 ohms, test or replace the Q2 A/C compressor clutch.

• If the test lamp illuminates

3. Verify a test lamp illuminates between the ignition circuit terminal 86 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF.

2. Test for less than 2 ohms in the ignition circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF.

2. Test for infinite resistance between the B+ circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, test or replace the KR29 A/C compressor clutch relay.

• If the test lamp illuminates

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

5. Verify the test lamp turns ON and OFF when commanding the Q2 A/C compressor clutch ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the harness connector at the K20 engine control module, ignition ON.

2. Test for less than 1 V between the control circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V

3. Ignition OFF.

4. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K20 engine control module.

• If the test lamp is always ON

1. Ignition OFF, disconnect the harness connector at the K20 engine control module.

2. Test for infinite resistance between the control circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, replace the K20 engine control module.

• If the test lamp turns ON and OFF

6. Test for less than 1 V between the control circuit terminal 87 and ground.

• If 1 V or greater
Repair the short to voltage on the circuit.

• If less than 1 V

7. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the Q2 A/C Compressor Clutch. It may take up to 2 minutes for all vehicle systems to power down.

8. Test for less than 10 ohms between the Q2 A/C compressor clutch ground circuit terminal A and ground.

• If 10 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 10 ohms

9. Connect the harness connector at the Q2 A/C compressor clutch.

10. Ignition ON, connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.

11. Verify the Q2 A/C compressor clutch is activated.

• If the Q2 A/C compressor clutch does not activate

1. Ignition OFF.

2. Test for less than 2 ohms in the control circuit terminal 87 end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, test or replace the Q2 A/C compressor clutch.

• If the Q2 A/C compressor clutch activates

12. Test or replace the KR29 A/C compressor clutch relay.

Repair Instructions

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

* Air Conditioning Clutch Assembly Replacement (LUV) Service and RepairAir Conditioning Clutch Assembly Replacement (LDE/LUW) Service and Repair

* Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)

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

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