A/C Signal Circuit Troubleshooting (Without Climate Control)

A/C Signal Circuit Troubleshooting

NOTE:

- Use this troubleshooting procedure if the A/C compressor, the A/C condenser fan, and radiator fan are inoperative.
- Before doing symptom troubleshooting, check for and resolve any powertrain DTCs, '07-09 models Initial Inspection and Diagnostic Overview, '10 model Initial Inspection and Diagnostic Overview.
- Check for B-CAN codes Reading and Clearing Diagnostic Trouble Codes.

1. Turn the ignition switch to ON (II).

2. Check if the blower motor operates at all speeds.

Does the blower motor operate at all speeds?

YES -

Go to step 3.

NO -

Repair the problem in the blower motor circuit.�

3. Using the HDS, confirm the following values in the PGM-FI Data List at idle.





Are all the values within specif ications?

YES -

Go to step 4.

NO -

Troubleshoot the value that is not within the specifications.�

4. Turn the ignition switch to LOCK (0).

5. Disconnect the HVAC control unit 28P connector.

6. Turn the ignition switch to ON (II).

7. Measure the voltage between the HVAC control unit 28P connector terminal No. 10 and body ground.





Is there battery voltage?

YES -

Go to step 14.

NO -

Go to step 8.

8. Turn the ignition switch to LOCK (0).

9. Disconnect the A/C compressor clutch 3P connector.

10. Turn the ignition switch to ON (II).

11. Measure the voltage between the A/C compressor clutch 3P connector terminal No. 1 and body ground.





Is there battery voltage?

YES -

Go to step 12.

NO -

Repair an open in the wire between the A/C compressor and the under-dash fuse/relay box. If the wire is OK, substitute a known-good under-dash fuse/relay box, and recheck. If the symptom goes away, replace the original under-dash fuse/relay box Under-dash Fuse/Relay Box Removal/Installation.�

12. Test the A/C compressor thermal protector Testing and Inspection.

Is the A/C compressor thermal protector OK?

YES -

Go to step 13.

NO -

Replace the A/C compressor thermal protector Service and Repair.�

13. Check for continuity between the HVAC control unit 28P connector terminal No. 10 and the A/C compressor clutch 3P connector terminal No. 2.





Is there continuity?

YES -

Check for loose wires or poor connections at the HVAC control unit 28P connector and at the A/C compressor clutch 3P connector. �

NO -

Repair an open in the wire between the HVAC control unit and A/C compressor.�

14. Turn the ignition switch to LOCK (0).

15. Measure the evaporator temperature sensor resistance between the HVAC control unit 28P connector terminals No. 9 and No. 19.





Is the resistance less than 24 kOhms?

YES -

Check for loose wires or poor connections at the HVAC control unit 28P connector. If the connections are good, substitute a known-good HVAC control unit, and recheck. If the symptom goes away, replace the original HVAC control unit HVAC Control Unit Removal/Installation (Without Climate Control).

NO -

Test the evaporator temperature sensor Evaporator Temperature Sensor Test.