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.
Circuit/System Description
When the A/C switch is pressed, the HVAC control assembly sends a serial data message to the engine control module (ECM) for an A/C request. This input will request the ECM to ground the A/C compressor clutch relay control circuit, which will switch the A/C CLTCH 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 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 4760 RPM.
* Engine speed is more than 600 RPM.
* A/C high side pressure is between 2929-269 kPa (425-39 psi).
* Throttle position is less than 100 percent.
* Evaporator temperature is greater than 0°C (32°F).
* ECM does not detect excessive torque load.
* ECM does not detect insufficient idle quality.
Reference Information
Schematic Reference
HVAC Schematics HVAC - Manual
Connector End View Reference
Component Connector End Views 1-2 Shift Solenoid (SS) Valve (MN5)
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 Programming and Relearning for scan tool information
Circuit/System Testing
1. Ignition OFF, disconnect the X1 harness connector at X50A fuse block-underhood.
2. Remove the control circuit terminal 46 using the correct terminal release tool, connect the X1 harness connector to the X50A fuse block-underhood.
3. Connect a test lamp between the control circuit terminal 46 and B+, engine running.
4. 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 ECM.
• 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
5. Ignition OFF and all vehicle systems OFF, connect the harness connector at the X50A fuse block-underhood, 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.
6. Test for less than 10 ohms between the Q2 A/C compressor clutch ground 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
7. Connect a test lamp between the control circuit terminal B and ground.
8. 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 and the circuit fuse is good
1. Ignition OFF, disconnect the X1 harness connector at the X50A fuse block-underhood.
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, replace the X50A fuse block-underhood.
• If the test lamp is always OFF and the circuit fuse is open
1. Ignition OFF
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 Q2 A/C compressor clutch.
• If the test lamp is always ON
1. Ignition OFF, disconnect the X1 harness connector at the X50A fuse block-underhood, Ignition ON.
2. Test for less then 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, replace the X50A fuse block-underhood.
• If the test lamp turns ON and OFF
9. Replace the Q2 A/C compressor clutch.
Component Testing
1. Ignition OFF, disconnect the A/C COMP relay.
2. Test for 60-180 ohms between terminals 85 and 86.
• If the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If not the specified value, replace the relay.
4. Install a 30-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.
• If greater than the specified range, replace the relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Air Conditioning Clutch Assembly Replacement Service and Repair
* Control Module References Programming and Relearning for HVAC and ECM replacement, setup and programming