A/C Pressure Switch Circuit Troubleshooting
A/C Pressure Switch Circuit Troubleshooting1. Disconnect the A/C compressor clutch 3P connector.
2. Turn the ignition switch ON (II).
3. Measure the voltage between the A/C compressor clutch 3P connector terminals No. 3 and body ground.
Is there about 5 V?
YES - Go to step 4.
NO - Check for loose or poor connections at the ECM/PCM, or repair open in the BLU/WHT wire between the A/C compressor and the ECM/PCM connector E (31P). If the wire is OK, substitute a known-good ECM/PCM and recheck. If the symptom goes away, replace the original ECM/PCM.
4. Turn the ignition switch OFF.
5. Test the A/C compressor thermal protector.
Is the A/C compressor thermal protector OK?
YES - Go to step 6.
NO - Replace the A/C compressor thermal protector.
6. Reconnect the A/C compressor clutch 3P connector.
7. Disconnect the A/C pressure switch 2P connector.
8. Turn the ignition switch ON (II).
9. Measure the voltage between the No. 2 terminal of the A/C pressure switch 2P connector and body ground.
Is there about 5 V?
YES - Go to step 10.
NO - Repair open in the WHT/BLU wire between the A/C pressure switch and the thermal protector.
10. Turn the ignition switch OFF.
11. Check for continuity between the No. 1 and No. 2 terminals of the A/C pressure switch.
Is there continuity?
YES - Go to step 12.
NO - Go to step 34.
12. Reconnect the A/C pressure switch 2P connector.
13. Disconnect the A/C switch 13P connector.
14. Turn the ignition switch ON (II).
15. Measure the voltage between the No. 8 terminal of the A/C switch 13P connector and body ground.
Is there about 5 V?
YES - Go to step 16.
NO - Repair open in the wire between the A/C pressure switch and the A/C switch.
16. Turn the ignition switch OFF.
17. Test the A/C switch.
Is the A/C switch OK?
YES - Go to step 18.
NO - Replace the A/C switch.
18. Disconnect the mode control switch 4P connector.
19. Turn the ignition switch ON (II).
20. Measure the voltage between the No. 3 terminal of the mode control switch 4P connector and body ground.
Is there about 5 V?
YES - Go to step 21.
NO - Repair open in the wire between the A/C pressure switch and the mode control switch.
21. Turn the ignition switch OFF.
22. Test the mode control switch.
Is the mode control switch OK?
YES - Go to step 23.
NO - Replace the heater-A/C control panel.
23. Disconnect the heater fan switch 7P connector.
24. Check for continuity between the No. 7 terminal of the A/C switch 13P connector and the No. 6 terminal of the heater fan switch 7P connector.
Is there continuity?
YES - Go to step 25.
NO - Repair open in the wire between the A/C switch and the heater fan switch.
25. Check for continuity between the No. 4 terminal of the mode control switch 4P connector and No. 6 terminal of the heater fan switch 7P connector.
Is there continuity?
YES - Go to step 26.
NO - Repair open in the wire between the mode control switch and the heater fan switch.
26. Test the heater fan switch.
Is the heater fan switch OK?
YES - Go to step 27.
NO - Replace the heater fan switch.
27. Check for continuity between the No. 3 terminal of the heater fan switch 7P connector and body ground.
Is there continuity?
YES - Go to step 28.
NO - Check for an open in the wire between the heater fan switch and body ground. If the wire is OK, check for poor ground at G402.
28. Disconnect the evaporator temperature sensor 2P connector.
29. Measure the resistance between the No. 1 and No. 2 terminals of the evaporator temperature sensor.
Is the resistance within the specifications shown on the graph?
YES - Go to step 30.
NO - Replace the evaporator temperature sensor.
30. Jump the SCS line with the HDS.
31. Disconnect ECM/PCM connector E (31P).
32. Check for continuity between the following terminals of ECM/PCM connector E (31P) and the evaporator temperature sensor 2P connector.
Is there continuity?
YES - Go to step 33.
NO - Repair any open in the wire(s) between the ECM/PCM and the evaporator temperature sensor.
33. Check for continuity between the No. 6 terminal of ECM/PCM connector E (31P) 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 E (31P), the evaporator temperature sensor 2P connector, the A/C pressure switch 2P connector, the A/C switch 13P connector, mode control switch 4P connector and at the heater fan switch 7P 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.
34. Check for proper A/C system pressure.
Is the pressure within specifications?
YES - Replace the A/C pressure switch.
NO - Repair the A/C pressure problem.