Orlando

Air Conditioning Compressor Malfunction

When the A/C switch is pressed, the HVAC control module sends an A/C request message to the engine control module (ECM) via CAN-Bus. Therefore the ECM grounds the A/C compressor clutch relay control circuit, which will switch the A/C compressor clutch relay. With the relay contacts closed, battery voltage is supplied to the A/C compressor clutch. The A/C compressor clutch will be activated.

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

Schematic Reference

HVAC Schematics : Automatic

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Note: Before executing Circuit/System Testing, all conditions shown in Diagnostic Aids must be met.

1. Ignition ON, activate and deactivate the A/C switch. Verify the scan tool A/C Switch parameter changes between Active and Inactive.

⇒	If the parameter does not change

Replace the A26 HVAC Controls.

⇓	If the parameter changes

2. Activate and deactivate the A/C switch. Verify the engine control module (ECM) scan tool A/C Request Signal parameter changes between Active and Inactive.

⇒	If the parameter does not change

Replace the K33 HVAC Control Module.

⇓	If the parameter changes

3. Ignition OFF, remove the KR29 A/C Compressor Clutch Relay.
4. Ignition ON, verify that 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

4.1.	Ignition OFF.

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

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, 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

4.1.	Ignition OFF.

4.2.	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

4.3.	Disconnect the harness connector at the Q2 A/C Compressor Clutch.

4.4.	Test for infinite resistance between the control circuit terminal 87 and ground.

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

⇓	If infinite resistance

4.5.	Connect the harness connector at the Q2 A/C Compressor Clutch.

4.6.	Install a 10 A fused jumper wire between B+ and the control circuit terminal 87 and verify the fuse is good.

⇒	If the fuse is open, replace the Q2 A/C Compressor Clutch.

⇒	If the fuse is good, replace the KR29 A/C Compressor Clutch Relay.

⇓	If the test lamp illuminates

5. 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

6. Ignition ON, connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the Q2 A/C Compressor Clutch is activated.

⇒	If the Q2 A/C Compressor Clutch is not activated

6.1.	Ignition OFF, disconnect the harness connector at the Q2 A/C Compressor Clutch.

6.2.	Test for less than 5 Ω between the ground circuit terminal A and ground.

⇒	If greater than 5 Ω, repair the open/high resistance in the circuit.

⇓	If less than 5 Ω

6.3.	Test for less than 2 Ω in the control circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the Q2 A/C Compressor Clutch.

⇓	If the Q2 A/C Compressor Clutch is activated

7. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86.
8. Command the engine control module (ECM) A/C Relay output function ON and OFF with the scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp always illuminates or does not illuminate

Replace the K20 Engine Control Module.

⇓	If the test lamp illuminates as commanded

9. Replace the KR29 A/C Compressor Clutch Relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.