A/C Signal Circuit Troubleshooting, HVAC
A/C Signal Circuit TroubleshootingNOTE:
- Do not use this troubleshooting procedure if any of the following items are operative: A/C condenser fan, radiator fan, A/C compressor. Refer to the symptom troubleshooting index. Symptom Related Diagnostic Procedures
- Before doing any symptom troubleshooting, check for powertrain DTCs.
1. Connect the HDS to the DLC.
2. Start the engine.
3. Turn on the A/C.
4. Check the blower motor operates at all speeds.
Does the blower motor operate at all speeds?
YES - Go to step 5.
NO - Repair the problem in the blower motor circuit.
5. Check the A/C SWITCH in the PGM-FI Data List with the HDS.
Is the A/C SWITCH on?
YES - The A/C signal is OK at this time.
NO - Go to step 6.
6. Turn the ignition switch OFF.
7. Disconnect the climate control unit connector A (24P).
8. Measure the evaporator temperature sensor resistance between the climate control unit connector A (24P) terminals No. 13 and No. 18.
Is the resistance less than 24 kohms?
YES - Go to step 9.
NO - Test the evaporator temperature sensor.
9. Turn the ignition switch ON (II).
10. Measure the voltage between the climate control unit connector A (24P) terminal No. 17 and body ground.
Is there battery voltage?
YES - Go to step 11.
NO - Repair open in the wire between the climate control unit and the MICU.
11. Turn the ignition switch OFF.
12. Reconnect the climate control unit connector A (24P).
13. Set the A/C button and fan control switch to ON, then turn the ignition switch ON (II).
14. Measure the voltage between the climate control unit connector A (24P) terminal No. 17 and body ground.
Is there 0.5 V or less?
YES - Replace the MICU.
NO - Check for loose wires or poor connections at the climate control unit connector A (24P). 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.