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 grounds the A/C request signal circuit. This input will request the ECM to ground the A/C compressor clutch relay control circuit, which will switch the A/C compressor clutch relay on. 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 ECM to turn on the compressor clutch:
* Battery voltage is between 9-18 volts
* Engine coolant temperature (ECT) is less than 123°C (253°F)
* Engine speed is greater than 600 RPM
* Engine speed is less than 4,760 RPM
* A/C high side pressure is between 2929-269 kPa (39-425 psi)
* Throttle position is less than 100 percent
* Evaporator temperature is greater than 2°C (34°F)
* ECM does not detect excessive 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 - Automatic
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation
* Air Temperature Description and Operation Air Temperature
* Air Delivery Description and Operation Air Delivery
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
Circuit/System Verification
Ignition ON, command the A/C Relay ON and OFF with a scan tool. Feel/listen for the A/C relay to click.
Circuit/System Testing
1. Ignition OFF, disconnect the A/C compressor relay.
2. Ignition ON.
3. Verify that a test lamp illuminates between the ignition circuit terminal 86 and ground.
• If the test lamp does not illuminate
Repair the open/high resistance in the circuit.
• If the test lamp illuminates
4. Verify that a test lamp illuminates between the relay B+ circuit terminal 30 and ground.
• If the test lamp does not illuminate
Replace the underhood fuse block.
• If the test lamp illuminates
5. Connect a test lamp between the ignition circuit terminal 86 and the control circuit terminal 85.
6. Verify the test lamp turns ON and OFF when commanding the A/C relay ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the X1 harness connector at the 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 engine control module.
• If the test lamp is always ON
5. Ignition OFF, disconnect the X1 harness connector at the engine control module.
6. 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 engine control module.
• If the test lamp turns ON and OFF
7. Verify that a test lamp does not illuminate between the control circuit terminal 87 and ground.
• If the test lamp illuminates
Repair the short to voltage on the circuit.
• If the test lamp does not illuminate
8. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the A/C compressor clutch. It may take up to 2 minutes for all vehicle systems to power down.
9. Test for less than 5 ohms between the ground circuit terminal A and ground.
• If 5 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 ground circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
10. Connect the harness connector at the A/C compressor clutch.
11. Ignition ON, connect a 10 A fused jumper wire between the B+ circuit terminal 30 and control circuit terminal 87.
12. Verify the A/C compressor clutch is activated.
• If the A/C compressor clutch does not activate
1. Ignition OFF.
2. 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, test or replace the A/C compressor clutch.
• If the A/C compressor clutch activates
13. Test or replace the A/C compressor relay.
Component Testing
1. Ignition OFF, disconnect the A/C compressor relay.
2. Test for 60-180 ohms between terminals 85 and 86.
• If less than 60 ohms or greater than 180 ohms
Replace the A/C compressor relay.
• If between 60-180 ohms
3. Test for infinite resistance between the terminals listed below:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If less than infinite resistance
Replace the A/C compressor relay.
• If infinite resistance
4. Install a 30 A fused jumper wire between relay terminal 86 and 12 V. Install a jumper wire between relay terminal 85 and ground. Test for less than 2 ohms between terminals 30 and 87.
5. Test for less than 2 ohms between terminals 30 and 87.
• If 2 ohms or greater
Replace the A/C compressor relay.
• If less than 2 ohms
6. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Air Conditioning Compressor Replacement (LU3) Removal and ReplacementAir Conditioning Compressor Replacement (LZ1, L20, LC9, L9H, L92, LMG) Removal and ReplacementAir Conditioning Compressor Replacement (LGH, LML) Removal and Replacement
* Compressor Clutch Plate/Hub Assembly Replacement Service and Repair
* Control Module References Control Module References for HVAC control module and ECM replacement, programming, and setup.