A/C Pressure Switch Circuit Troubleshooting (With A/C)

A/C Pressure Switch Circuit Troubleshooting

NOTE:

- Do not use this troubleshooting procedure if any of the following items are operative; the condenser fan, the radiator fan, the A/C compressor, or if the heater is inoperative. Refer to the symptom troubleshooting index.

- Check the A/C high-side pressure.

1. Disconnect the A/C pressure switch 2P connector.

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

3. Measure the voltage between A/C pressure switch 2P connector terminal No. 2 and body ground.

Is there battery voltage?
YES - Go to step 4.

NO - Go to step 20.






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

5. Check for continuity between A/C pressure switch terminals No. 1 and No. 2.

Is there continuity?
YES - Go to step 6.

NO - Replace the A/C pressure switch.






6. Reconnect the A/C pressure switch 2P connector.

7. Disconnect the A/C switch 5P connector.

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

9. Measure the voltage between A/C switch 5P connector terminal No. 2 and body ground.

Is there battery voltage?
YES - Go to step 10.

NO - Repair open in the wire between the A/C pressure switch and the A/C switch.






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

11. Test the A/C switch. A/C Switch Test (With A/C)

Is the A/C switch OK?
YES - Go to step 12.

NO - Replace the A/C switch. Service and Repair


12. Disconnect the heater fan switch 8P connector.

13. Check for continuity between A/C switch 5P connector terminal No. 1 and heater fan switch 8P connector terminal No. 6.

Is there continuity?
YES - Go to step 14.

NO - Repair open in the wire between the A/C switch and the heater fan switch.






14. Test the heater fan switch. Heater Fan Switch Test

Is the heater fan switch OK?
YES - Go to step 15.

NO - Replace the heater fan switch. Overhaul


15. Remove the evaporator temperature sensor Service and Repair and test it. Evaporator Temperature Sensor Test (With A/C)

Is the evaporator temperature sensor OK?
YES - Go to step 16.

NO - Replace the evaporator temperature sensor. Service and Repair


16. Jump the SCS line with the HDS.
NOTE: This step must be done to protect engine/powertrain control module (ECM/PCM) from damage.

17. Disconnect ECM/PCM connector A (49P).

18. Check for continuity between the following terminals of ECM/PCM connector A (49P) and the evaporator temperature sensor 2P connector.





Is there continuity?
YES - Go to step 19.

NO - Repair open in the wire(s) between the ECM/PCM and the evaporator temperature sensor.






19. Check for continuity between ECM/PCM connector A (49P) terminal No. 38 and body ground.

Is there continuity?
YES - Repair short to body ground in the wire between the ECM/PCM and the evaporator temperature sensor.

NO - Check for loose wires or poor connections at ECM/PCM connector A (49P), the evaporator temperature sensor 2P connector, the A/C pressure switch 2P connector, the A/C switch 5P connector, and at the heater fan switch 8P connector. If the connections are good, substitute a known-good ECM/PCM, and recheck. If the symptom/indication goes away, replace the original ECM/PCM.






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

21. Reconnect the A/C pressure switch 2P connector.

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

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

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

Is there battery voltage?
YES - Go to step 25.

NO - Go to step 27.






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

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

Is the A/C compressor thermal protector OK?
YES - Repair open in the wire between the A/C compressor clutch and the A/C pressure switch.

NO - Replace the A/C compressor thermal protector. A/C Compressor Thermal Protector Replacement (With A/C)


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

28. Reconnect the A/C pressure switch 3P connector.

29. Make sure the A/C switch is OFF.

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

31. Measure the voltage between under-dash fuse/relay box connector A (36P) terminal No. 21 and body ground with the under-dash fuse/relay box connectors connected.

Is there battery voltage?
YES - Repair open in the wire between the A/C compressor and the MICU.

NO - Check for loose wires or poor connections at the under-dash fuse/relay box. If the connections are OK, substitute a known-good MICU and recheck. If the symptom goes away, replace the original MICU.