A/C Signal Circuit Troubleshooting

A/C Signal Circuit Troubleshooting

1. Start the engine, and let it idle.

2. Turn the blower switch on.

3. Turn the A/C switch on.

4. Check the A/C CLUTCH in the DATA LIST with the HDS.

Does it indicate ON?
YES - Go to step 5.

NO - Go to the A/C pressure switch circuit troubleshooting. A/C Pressure Switch Circuit Troubleshooting (With A/C)


5. Check the A/C system.

Does the A/C system operate?
YES - The air conditioning system circuit is OK.

NO - Go to step 6.


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

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

8. Activate the A/C CLUTCH in the INSPECTION MENU with the HDS.

Is there a clicking noise from the A/C compressor clutch?
YES - Do the A/C system test. A/C System Test (With A/C)

NO - Go to step 9.


9. Momentarily connect under-hood fuse/relay box 16P connector terminal No. 11 to body ground with a jumper wire several times.

Is there clicking noise from the A/C compressor clutch?
YES - Repair open in the wire between the ECM (E18) and the A/C clutch relay.

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