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Pinpoint Test J: The Air Conditioning (A/C) Is Always On

WARNING: This page is about a different car, the 2006 Mercury Milan, 2006 Lincoln Zephyr, and 2006 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: When disconnecting and reconnecting the pressure transducer electrical connector, make sure that the connector-locking device is in place and that the locking device and connector are correctly and fully seated.
  1. J1 CHECK THE A/C PRESSURE PCM PID 
    • Key in ON position.
    • Enter the following diagnostic mode on the scan tool: A/C Pressure PCM PID.
    • With the manifold gauge set connected, compare the pressure readings of the manifold gauge set and the A/C pressure PID.
    • Are the pressure values of the manifold gauge set and the A/C pressure PID similar? 

    Yes  : GO to J2.

    No  : INSTALL a new A/C pressure transducer. TEST the system for normal operation.

  2. J2 CHECK THE A/C EVAPORATOR TEMPERATURE PID 
    • Allow the vehicle exterior and interior to stabilize to an ambient temperature above 16°C (60°F).
    • Enter the following diagnostic mode on the scan tool: A/C Evaporator Discharge Temperature PCM PID.
    • Does the A/C evaporator discharge temperature PID read similar to the ambient temperature? 

    Yes  : GO to J3.

    No  : INSTALL a new A/C evaporator discharge temperature sensor. TEST the system for normal operation.

  3. J3 CHECK THE A/C REQUEST PID WITH THE A/C OFF 
    • Enter the following diagnostic mode on the scan tool: PCM A/C REQUEST PID.
    • Does the PCM A/C REQUEST PID read ON? 

    Yes  : DATC/EATC, GO to J4.

    EMTC, GO to  J5.

    No  : GO to  J7.

  4. J4 CHECK THE A/C SWITCH PID WITH THE A/C OFF 
    • Enter the following diagnostic mode on the scan tool: PCM A/C SWITCH PID.
    • Does the PCM A/C SWITCH PID read ON? 

    Yes  : GO to  J10.

    No  : GO to  J11.

  5. J5 CHECK EMTC A/C REQUEST OUTPUT 
    • Key in OFF position.
    • Disconnect: IC C220.
    • Key in ON position.
    • Select the OFF position on the EMTC module.
    • Measure the resistance between IC C220-23, circuit CH434 (GY/YE) and ground.
      Fig 1: Checking EMTC A/C Request Output
      G04682451Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 

    Yes  : GO to J6.

    No  : GO to  J11.

  6. J6 CHECK CIRCUIT CH434 (GY/YE) FOR A SHORT TO GROUND 
    • Key in OFF position.
    • Disconnect: EMTC C2357a.
    • Key in ON position.
    • Measure the resistance between IC C220-23, circuit CH434 (GY/YE) and ground.
      Fig 2: Checking Circuit CH434 (GY/YE) For Short To Ground
      G04682452Courtesy of FORD MOTOR CO.
    • Is the resistance greater than 10,000 ohms? 

    Yes  : GO to  J10.

    No  : REPAIR circuit CH434 (GY/YE) for a short to ground. TEST the system for normal operation.

  7. J7 CHECK A/C CLUTCH RELAY PID WITH THE A/C OFF 
    • Enter the following diagnostic mode on the scan tool: PCM A/C CLUTCH RELAY PID.
    • Does the PCM A/C CLUTCH RELAY PID read ON? 

    Yes  : REFER to INTRODUCTION - GASOLINE article.

    No  : GO to J8.

  8. J8 CHECK FOR VOLTAGE TO THE A/C COMPRESSOR CLUTCH FIELD COIL 
    • Key in OFF position.
    • Disconnect: A/C Compressor Clutch Field Coil C100.
    • Key in ON position.
    • Select the OFF position on the EMTC module.
    • Measure the voltage between A/C compressor clutch field coil C100-B, circuit CH401 (VT/WH) and ground.
      Fig 3: Checking For Voltage To A/C Compressor Clutch Field Coil
      G04682453Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 

    Yes  : GO to J9.

    No  : ADJUST the A/C compressor clutch gap. REFER to AIR CONDITIONING (A/C) CLUTCH AIR GAP ADJUSTMENT . TEST the system for normal operation.

  9. J9 CHECK CIRCUIT CH401 (VT/WH) FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: A/C Clutch Relay.
    • Key in ON position.
    • Measure the voltage between A/C compressor clutch field coil C100-B, circuit CH401 (VT/WH) and ground.
      Fig 4: Checking Circuit CH401 (VT/WH) For Short To Voltage
      G04682454Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 

    Yes  : REPAIR circuit CH401 (VT/WH) for a short to voltage. TEST the system for normal operation.

    No  : INSTALL a new A/C clutch relay. Check the A/C clutch diode. INSTALL a new diode if necessary. TEST the system for normal operation.

  10. J10 CHECK THE MODULE CONNECTION 

    Yes  : INSTALL a new DATC/EATC module. REFER to CLIMATE CONTROL . TEST the system for normal operation.

    No  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

  11. J11 CHECK THE PCM MODULE CONNECTION 
    • Clear the DTCs.
    • Disconnect all the PCM connectors.
    • Check For:
      • Corrosion.
      • Pushed-out pins.
      • Incorrectly seated connector.
    • Connect and correctly seat all the PCM connectors.
    • Operate the system.
    • Does the concern return? 

    Yes  : INSTALL a new PCM. TEST the system for normal operation.

    No  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.

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