A/C Pressure Switch Circuit Troubleshooting
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.
- Before doing any symptom troubleshooting, check for powertrain DTCs Initial Inspection and Diagnostic Overview.
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 an 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.
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 an 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.
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 control module/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 an 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 a 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 an 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.�
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 an 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.�