A/C Signal Circuit Troubleshooting

• 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.
  
• Before performing symptom troubleshooting, check for powertrain DTCs, except K20Z2 engine, K20Z2 engine.
  

1.	Turn the ignition switch OFF.

2.	Disconnect the HVAC control unit 24P connector.

3.	Turn the ignition switch ON (II).

4.	Measure the voltage between the HVAC control unit 24P connector terminal No. 11 and body ground.   Is there battery voltage? YES - Go to 5. NO - Repair open in the wire beyween the HVAC control unit and the MICU.n

5.	Turn the ignition switch OFF.

6.	Measure the evaporator temperature sensor resistance between the HVAC control unit 24P connector terminals No. 2 and No. 13.   Is the resistance less than 24k W? YES - Go to 7. NO - Test the evaporator temperature sensor.n

7.	Reconnect the HVAC control unit 24P connector.

8.	Turn the ignition switch ON (II).

9.

Check the blower motor operates at all speeds. Does the blower motor operate at all speeds? YES - Check for loose wires or poor connections at the HVAC control unit 24P connector. If the connections are good, substitute a known-good HVAC control unit and recheck. If the sympton goes away, relace the original  HVAC control unit.n NO - Repair the problem in the blower motor circuit.n