## A/C Pressure Switch Circuit Troubleshooting

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

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

3. | 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 4. NO - Go to 22.

4. | Turn the ignition switch OFF.

5. | Check for continuity between the No. 1 and No. 2 terminals of the A/C pressure switch. Is there continuity? YES - Go to 6. NO - Go to 27.

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

7. | Disconnect the A/C thermostat 3P connector.

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

9. | Measure the voltage between the No. 3 terminal of the A/C thermostat 3P connector and body ground. Is there battery voltage? YES - Go to 10. NO - Repair open in the wire between the No. 22 fuse in the under-dash fuse/relay box and the A/C thermostat.n

10. | Turn the ignition switch OFF.

11. | Test the A/C thermostat. Is the A/C thermostat OK? YES - Go to 12. NO - Replace the A/C thermostat.n

12. | Reconnect the A/C thermostat 3P connector.

13. | Disconnect the A/C switch 5P connector.

14. | Turn the ignition switch ON (II).

15. | Measure the voltage between the No. 2 terminal of the A/C switch 5P connector and body ground. Is there about 5 V? YES - Go to 16. NO - Repair open in the wire between the A/C thermostat and the A/C switch.n

16. | Turn the ignition switch OFF.

17. | Test the A/C switch. Is the A/C switch OK? YES - Go to 18. NO - Replace the A/C switch.n

18. | Disconnect the heater fan switch 7P connector.

19. | Check for continuity between the No. 1 terminal of the A/C switch 5P connector and the No. 6 terminal of the heater fan switch 7P connector. Is there continuity? YES - Go to 20. NO - Repair open in the wire between the A/C switch and the heater fan switch.n

20. | Test the heater fan switch. Is the heater fan switch OK? YES - Go to 21. NO - Replace the heater fan switch.n

21. | Check for continuity between the No. 3 terminal of the heater fan switch 7P connector and body ground. Is there continuity? YES - Check for loose wires or poor connections at ECM connector E (40P), the A/C thermostat connector, the A/C pressure switch 2P connector, the A/C switch 5P connector and at the heater fan switch 7P connector. If the connections are good, substitute a known-good ECM, and recheck. If the symptom/indication goes away, replace the original ECM.n 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.n

22. | Turn the ignition switch OFF.

23. | Reconnect the A/C pressure switch 2P connector.

24. | Make sure the A/C switch is OFF.

25. | Turn the ignition switch ON (II).

26. | Measure the voltage between the No. 40 terminal of ECM connector E (40P) and body ground with the ECM connectors connected. Is there about 5 V? YES - Repair open in the wire between the ECM and the A/C pressure switch.n NO - Check for loose wires or poor connections at ECM connector E (40P). If the connections are good, substitute a known-good ECM, and recheck. If the symptom/indication goes away, replace the original ECM.n

27. | Check for proper A/C system pressure. Is the pressure within specifications? YES - Replace the A/C pressure switch.n NO - Repair the A/C pressure problem.n