Spark

Air Conditioning Compressor Malfunction

When the A/C switch is pressed, the HVAC control assembly sends a 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 clutch relay. With the relay contacts closed, battery voltage is supplied to the A/C compressor clutch assembly.

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

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

Control Module References for scan tool information

1. Ignition OFF, disconnect the KR29 A/C COMP relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 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 ignition circuit terminal 85 and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or a open/high resistance. If the circuit tests normal and ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.

4. Verify that a test lamp illuminates between the relay B+ circuit terminal 30 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 B+ circuit fuse is open, replace the KR29 A/C Clutch Relay.

5. Disconnect the harness connector at the Q2 A/C Compressor Clutch.
6. Test for less than 1 Ω between the ground circuit terminal A and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

7. Connect the harness connector at the Q2 A/C Compressor Clutch.
8. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and control circuit terminal 87. Verify the A/C compressor clutch is activated.

⇒	If the A/C clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the Q2 A/C Compressor Clutch.

9. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86.
10. Command the A/C Relay output function 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 K20 Engine Control Module.

⇒	If the test lamp is always OFF, test the control circuit for a short circuit to voltage, or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

11. If all circuits test normal, test or replace the KR29 A/C clutch relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.