Refrigerant Pressure Sensor / Switch: Testing and Inspection

A/C Pressure Switch Circuit Troubleshooting

NOTE:
^ Do not use this troubleshooting procedure if any of the following items are operative; A/C condenser fan, radiator fan, A/C compressor, or if the heater is inoperative. Refer to the Symptom Troubleshooting Index.
^ Before performing symptom troubleshooting, check for powertrain DTCs.

1. Disconnect the thermal protector 3P connector.

2. Turn the ignition switch ON (II).





3. Measure the voltage between the No.3 terminal of the thermal protector 3P connector and body ground.

Is there about 5 V?

YES-Go to step 4.

NO-Go to step 19.

4. Turn the ignition switch OFF.





5. Check for continuity between the No.2 and No.3 terminals of the thermal protector.

Is there continuity?

YES-Go to step 6.

NO-Replace the thermal protector.E

6. Reconnect the thermal protector 3P connector.

7. Disconnect the NC 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 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 21.

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

13. Disconnect climate control unit connector A (20P).

14. Turn the ignition switch ON (II).





15. Measure the voltage between the No. 6 terminal of climate control unit connector A (20P) and body ground.

Is there about 5 V?

YES-Go to step 16.

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

16. Turn the ignition switch OFF.

17. Disconnect climate control unit connector B (22P).





18. Measure the resistance of the evaporator temperature sensor between the No. 7 and No. 9 terminals of climate control unit connector B (22P).

Is the resistance less than 24 k Ohms?

YES-Check for loose wire or poor connections at climate control unit connector B (22P) and at the thermal protector 3P connector and at the A/C pressure switch 2P connector. If the connections are good, substitute a known-good climate control unit, and recheck. If the symptom/indication goes away, replace the original climate control unit.

NO-Test the evaporator temperature sensor.

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





20. Using the backprobe set, measure the voltage between the No. 28 terminal of ECM connector E (31 P) and body ground with the ECM connectors connected.

Is there about 5 V?

YES-Repair open in the wire between the ECM and the thermal protector.

NO-Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.

21. Check for proper A/C system pressure.

Is the pressure within specifications?

YES-Replace the NC pressure switch.

NO-Repair the NC pressure problem.