A/C Pressure Switch Circuit Troubleshooting

A/C Pressure Switch Circuit Troubleshooting

NOTE:

- Do not use this troubleshooting procedure if any of these items are working properly with the A/C button ON; A/C condenser fan, radiator fan and A/C compressor, or the heater does not work. Refer to the symptom troubleshooting index.
- Before doing symptom troubleshooting, do the self-diagnostic function Initial Inspection and Diagnostic Overview.

1. Turn the ignition switch to ON (II).

2. Turn the blower switch on, and check for blower motor operation.

Does the blower motor run correctly on all speeds?

YES -

Go to step 3.

NO -

Troubleshoot the blower motor circuit HVAC.�

3. Turn the ignition switch to LOCK (0).

4. Disconnect the A/C pressure switch 2P connector.

5. Turn the ignition switch to ON (II).

6. Measure the voltage between A/C pressure switch 2P connector terminal No. 2 and body ground.





Is there battery voltage?

YES -

Go to step 7.

NO -

Go to step 15.

7. Turn the ignition switch to LOCK (0).

8. Check for continuity between A/C pressure switch terminals No. 1 and No. 2.





Is there continuity?

YES -

Go to step 9.

NO -

Go to step 17.

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

10. Disconnect the heater control panel 30P connector.

11. Turn the ignition switch to ON (II).

12. Measure the voltage between heater control panel 30P connector terminal No. 7 and body ground.





Is there battery voltage?

YES -

Go to step 13.

NO -

Repair an open in the wire between the heater control panel and the A/C pressure switch.�

13. Turn the ignition switch to LOCK (0).

14. Measure the resistance between heater control panel 30P connector terminals No. 13 and No. 28.





Is the resistance less than 24 kOhms?

YES -

Check for loose wires or poor connections at the heater control panel 30P connector and at the A/C pressure switch 2P connector. If the connections are good, substitute a known-good heater control panel, and recheck. If the symptom/indication goes away, replace the original heater control panel Service and Repair.�

NO -

Test the evaporator temperature sensor Evaporator Temperature Sensor Test.�

15. Make sure the A/C button is OFF.

16. Measure the voltage between under-dash fuse/relay box connector F (12P) terminal No. 9 and body ground with the under-dash fuse/relay box connectors connected.





Is there 5 V or more?

YES -

Repair an open in the wire between the under-dash fuse/relay box and the A/C pressure switch.�

NO -

Troubleshoot the multiplex control system Multiplex Control System Troubleshooting.�

NOTE: Check for multiplex codes in mode 1. Follow the troubleshooting for any codes found. If no codes are found, substitute a known-good multiplex control unit and a ECM/PCM one at a time.

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.�