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Pinpoint Test L: The A/C Is Always On

WARNING: This page is about a different car, the 2004 Mercury Mountaineer and 2004 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

Test Step 

  1. L1 CHECK A/C CLUTCH RELAY FAULT PID WITH THE A/C OFF 
    • Key in ON position.
    • Place the function selector switch to the OFF position or press the OFF manual override button on the DATC module.
    • Enter the following diagnostic mode on the diagnostic tool: PCM A/C CLUTCH RELAY FAULT PID.
    • Does the PCM A/C CLUTCH RELAY FAULT PID read YES? 

    Yes 

    REPAIR circuit 331 (PK/YE). TEST the system for normal operation.

    No 

    GO to L2.

  2. L2 CHECK A/C REQUEST PID WITH THE A/C OFF 
    • Enter the following diagnostic mode on the diagnostic tool: PCM A/C REQUEST PID.
    • Does the PCM A/C REQUEST PID read ON? 

    Yes 

    For DATC systems, INSTALL a new DATC module. refer to CLIMATE CONTROL ASSEMBLY - DATC . TEST the system for normal operation.

    For manual climate control systems, GO to L3.

    No 

    GO to  L5.

  3. L3 CHECK CIRCUIT 348 (VT) FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: Climate Control Assembly C294a and C294b.
    • Disconnect: PCM C175a.
    • Key in ON position.
    • Measure the voltage between the climate control assembly C294b-9, circuit 348 (VT) and ground.
      Fig 1: Checking Circuit 348 (VT) For Short To Voltage
      G03182766Courtesy of FORD MOTOR CO.
    • Is voltage present? 

    Yes 

    REPAIR circuit 348 (VT). TEST the system for normal operation.

    No 

    GO to L4.

  4. L4 CHECK THE FUNCTION SELECTOR SWITCH 
    • Key in OFF position.
    • Carry out the FUNCTION SELECTOR SWITCH  component test.
    • Does the function selector switch test good? 

    Yes 

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

    No 

    INSTALL a new function selector switch. REFER to CLIMATE CONTROL ASSEMBLY - MANUAL . TEST the system for normal operation.

  5. L5 CHECK THE A/C CONTROL RELAY COIL VOLTAGE 
    • Key in OFF position.
    • Disconnect: A/C Control Relay.
    • Key in ON position.
    • With the engine running, measure the voltage between the A/C control relay socket pin 1, circuit 1139 (VT/YE) and socket pin 2, circuit 331 (PK/YE).
      Fig 2: Checking A/C Control Relay Coil Voltage
      G03182767Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 

    Yes 

    GO to L6.

    No 

    GO to  L7.

  6. L6 CHECK CIRCUIT 331 (PK/YE) FOR A SHORT TO GROUND 
    • Key in OFF position.
    • Disconnect: PCM C175a.
    • Measure the resistance between the A/C control relay socket pin 2, circuit 331 (PK/YE) and ground.
      Fig 3: Checking Circuit 331 (PK/YE) For Short To Ground
      G03182768Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 

    Yes 

    REPAIR circuit 331 (PK/YE) for a short to ground. TEST the system for normal operation.

    No 

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

  7. L7 CHECK THE A/C CONTROL RELAY 
    • Key in ON position.
    • With the engine running, place the function selector switch to the A/C position or press the DEFROST manual override button on the DATC module.
    • Does the A/C compressor operate? 

    Yes 

    GO to L8.

    No 

    INSTALL a new A/C control relay. TEST the system for normal operation.

  8. L8 CHECK FOR VOLTAGE TO THE A/C COMPRESSOR CLUTCH FIELD COIL 
    • Key in OFF position.
    • Disconnect: A/C Compressor Clutch Field Coil C1110.
    • Key in ON position.
    • Measure the voltage between the A/C compressor clutch field coil C1110-2, circuit 321 (GY/WH) and ground.
      Fig 4: Checking Voltage To A/C Compressor Clutch Field Coil
      G03182769Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 

    Yes 

    REPAIR circuit 321 (GY/WH) for a short to voltage. TEST the system for normal operation.

    No 

    GO to L9.

  9. L9 CHECK THE A/C COMPRESSOR CLUTCH AIR GAP 
    • Key in OFF position.
    • Measure the A/C compressor clutch air gap at three equally spaced locations between the clutch hub and the A/C compressor clutch pulley.
      Fig 5: Checking A/C Compressor Clutch Air Gap
      G03182770Courtesy of FORD MOTOR CO.
    • Is the A/C compressor clutch air gap greater than 0.75 mm (0.030 in)? 

    Yes 

    ADJUST the A/C compressor clutch field coil. REFER to AIR CONDITIONING (A/C) CLUTCH AIR GAP ADJUSTMENT . TEST the system for normal operation.

    No 

    INSTALL a new A/C compressor clutch field coil. REFER to AIR CONDITIONING (A/C) COMPRESSOR - 4.0L SOHC  or AIR CONDITIONING (A/C) COMPRESSOR - 4.6L (2V) . TEST the system for normal operation.

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