A/C Pressure Switch Circuit Troubleshooting - With Climate Control

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 18.


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 23.


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

7.Disconnect climate control unit connector A (12P).

8.Turn the ignition switch ON (II).

9.Measure the voltage between the No. 5 terminal of climate control unit connector A (12P) and body ground.

 

Is there about 5 V?


YES - Go to 10.


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


10.Turn the ignition switch OFF.

11.Disconnect the A/C switch 5P connector.

12.Turn the ignition switch ON (II).

13.Measure the voltage between the No. 2 terminal of the A/C switch 5P connector and body ground.

 

Is there battery voltage?


YES - Go to 14.


NO - Repair open in the wire between the No. 22 fuse in the under-dash relay box and the A/C switch.n


14.Turn the ignition switch OFF.

15.Test the A/C switch.

Is the A/C switch OK?


YES - Go to 16.


NO - Repair the  A/C switch.n


16.Check for continuity between the No. 2 terminal of climate control unit connector A (12P) and the No. 1 terminal of the A/C switch 5P connector.

 

Is there continuity?


YES - Go to 17.


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

17.Check for continuity between the No. 2 terminal of climate control unit connector A (12P) and body ground.

 

Is there continuity?


YES - Repair short to body ground in the wire between the climate control unit and the A/C switch.n


NO - Check for loose wires or poor connections at climate control unit connector A (12P), the A/C pressure switch 2P connector and at the A/C switch 5P 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.n

18.Turn the ignition switch OFF.

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

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

21.Turn the ignition switch ON (II).

22.Messure the voltage between the No. 28 terminal of ECM/PCM connector E (31P) and body ground with the ECM/PCM connectors connected.

 

Is there about 5 V?


YES - Repair open in the wire between the ECM/PCM and the A/C pressure switch.n


NO - Check for loose wires or poor connections at ECM/PCM connector E (31P) and at the A/C pressure switch 2P 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.n


23.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