Air Conditioning Compressor Malfunction
Air Conditioning Compressor Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
Ignition voltage is supplied directly to the A/C compressor clutch relay. The engine control module (ECM) controls the relay by grounding the A/C clutch relay control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. The driver has a fault line which is monitored by the ECM. When the ECM is commanding a component ON, the voltage of the control circuit should be near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage.
Diagnostic Aids
The following conditions must be met in order for the ECM to engage the A/C compressor clutch:
* Battery voltage is between 9-18 volts
* Engine coolant temperature (ECT) is less than 123°C (253°F)
* Engine speed is less than 4,760 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/PCM does not detect excessive torque load
* ECM/PCM does not detect insufficient idle quality
Reference Information
Schematic Reference
HVAC Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
* Air Temperature Description and Operation (Air Temperature Description and Operation)
* Air Delivery Description and Operation (Air Delivery Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for Scan Tool Information
Circuit/System Verification
Ignition ON, command the A/C relay ON and OFF with a scan tool. Observe the A/C compressor operation, the A/C compressor clutch should engage and disengage when changing between the commanded states.
Circuit/System Testing
1. Ignition OFF, disconnect the A/C CLTCH relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal and ground.
• If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the relay coil B+ circuit terminal and ground.
• If the test lamp does not illuminate, Refer to DTC B1428 (B1428).
4. Verify that a test lamp illuminates between the relay switch B+ circuit terminal and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ ignition circuit fuse is open, test the control circuit terminal for a short to ground.
5. Disconnect the harness connector at the A/C compressor clutch.
6. Test for less than 1.0 ohm of resistance between the A/C compressor clutch ground circuit terminal B and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the A/C compressor clutch.
8. Connect a 10A fused jumper wire between the relay switch B+ circuit terminal and the control circuit terminal. Verify the A/C compressor clutch is activated.
• If the A/C compressor clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the A/C compressor.
9. Connect a test lamp between the relay coil B+ circuit terminal and the A/C compressor clutch relay control circuit terminal.
10. Command the A/C relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
11. If all circuits test normal, test or replace the A/C CLTCH relay.
Component Testing
Relay Test
1. Ignition OFF, disconnect the A/C CLTCH relay.
2. Test for 60-180 ohms of resistance 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 of resistance 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.
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming