Air Conditioning Switch: Testing and Inspection
A/C Pressure Switch Circuit Troubleshooting1. 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 15.
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.
6. Disconnect the A/C pressure switch 2P connector.
7. Turn the ignition switch ON (II).
8. 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 9.
NO - Repair open in the wire between the A/C pressure switch and the thermal protector.
9. Turn the ignition switch OFF.
10. Check for continuity between the No.1 and No.2 terminals of the A/C pressure switch.
Is there continuity?
YES - Go to step 11.
NO - Go to step 17.
11. Reconnect the A/C pressure switch 2P connector.
12. Disconnect climate control unit connector A (20P).
13. Turn the ignition switch ON (II).
14. Measure the voltage between the No.6 terminal of climate control unit connector A (20P) and body ground.
Is there about 5 V?
YES - Check for loose wires or poor connections at climate control unit connector A (20P) 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 - Repair open in the wire between the climate control unit and the A/C pressure switch.
15. Make sure the A/C switch is OFF.
16. Using the back probe set, measure the voltage between the No.28 terminal of ECM connector E (31P) 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.
17. 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.