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