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Pinpoint Test D: The Air Conditioner (A/C) Is Always On

WARNING: This page is about a different car, the 2007 Mercury Mariner and 2007 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
  1. D1 RETRIEVE AND RECORD THE DTCs FROM THE CONTINUOUS AND ON DEMAND SELF-TEST-PCM 
    • Connect the diagnostic tool.
    • Make sure the function selector switch is in the OFF position.
    • Key in ON position.
    • Enter the following diagnostic mode on the diagnostic tool: PCM Self-Test
    • Retrieve and document the continuous DTCs.
    • Is DTC P1464 retrieved? 
    1. YES  : Go to  D2.
    2. NO  : Go to  D7.
  2. D2 CHECK THE A/C CYCLING SWITCH PID WITH THE A/C OFF 
    • Enter the following diagnostic mode on the diagnostic tool: PCM PIDs
    • Turn the function selector switch to the OFF position.
    • Monitor the PCM A/C cycling switch PID.
    • Does the PCM A/C cycling switch PID read ON? 
    1. YES  : Go to  D3.
    2. NO  : Go to  D7.
  3. D3 CHECK FOR A FALSE INPUT SIGNAL TO THE PCM 
    • Key in OFF position.
    • Disconnect: PCM C175b
    • Key in ON position.
    • Turn the function selector switch to the OFF position.
      • Fig 1: Checking Circuit For Voltage
      GF0025654Courtesy of FORD MOTOR CO.
    • Measure the voltage between PCM C175b-15, circuit 198 (DG/OG), harness side and ground.
    • Is the voltage greater than 10 volts? 
    1. YES  : Go to  D4.
    2. NO  : Go to  D6.
  4. D4 CHECK THE FUNCTION SELECTOR SWITCH FOR A SHORT TO POWER 
    • Key in OFF position.
    • Disconnect: Function Selector Switch C294a
    • Key in ON position.
    • Enter the following diagnostic mode on the diagnostic tool: PCM PIDs
    • Does the PCM A/C cycling switch PID read ON? 
    1. YES  : Go to  D5.
    2. NO  : INSTALL a new function selector switch. REFER to CLIMATE CONTROL article. TEST the system for normal operation.
  5. D5 CHECK CIRCUIT 348 (VT) FOR A SHORT TO POWER 
    • Key in OFF position.
    • Disconnect: A/C Cycling Switch C130
    • Key in ON position.
    • Enter the following diagnostic mode on the diagnostic tool: PCM PIDs
    • Does the PCM A/C cycling switch PID read ON? 
    1. YES  : Go to  D6.
    2. NO  : REPAIR the circuit. TEST the system for normal operation.
  6. D6 CHECK CIRCUIT 198 (DG/OG) FOR A SHORT TO POWER 
    • Key in OFF position.
    • Disconnect: Dual Pressure Switch C1062
    • Key in ON position.
    • Enter the following diagnostic mode on the diagnostic tool: PCM PIDs
    • Does the PCM A/C cycling switch PID read ON? 
    1. YES  : REPAIR circuit 198 (DG/OG). TEST the system for normal operation.
    2. NO  : REPAIR circuit 441 (RD/YE). TEST the system for normal operation.
  7. D7 CHECK FOR A SHORTED A/C CLUTCH RELAY 
    • Disconnect: A/C Clutch Relay C1008
    • Start the vehicle.
    • Observe the A/C compressor.
    • Is the A/C compressor clutch engaged? 
    1. YES  : CONNECT the A/C relay. Go to  D11 .
    2. NO  : Go to  D8.
  8. D8 CHECK A/C CLUTCH RELAY 
    • Carry out the A/C clutch relay component test. Refer to COMPONENT TESTING article.
    • Is the A/C clutch relay OK? 
    1. YES  : Go to  D9.
    2. NO  : INSTALL a new A/C clutch relay. TEST the system for normal operation.
  9. D9 CHECK CIRCUIT 331 (PK/YE) FOR A SHORT TO GROUND 
    • Key in OFF position.
    • Disconnect: PCM C175b
      • Fig 2: Checking Circuit For Short To Ground
      GF0025655Courtesy of FORD MOTOR CO.
    • Measure the resistance between A/C clutch relay C1008-2, circuit 331 (PK/YE), harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : REPAIR the circuit. TEST the system for normal operation.
    2. NO  : Go to  D10.
  10. D10 CHECK FOR CORRECT PCM OPERATION 
    • Disconnect all PCM connectors.
    • Check for:
      • corrosion.
      • pushed-out pins.
    • Connect all PCM connectors and make sure they seat correctly.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 
    1. YES  : INSTALL a new PCM. REFER to ELECTRONIC ENGINE CONTROLS - 2.3L article or ELECTRONIC ENGINE CONTROLS - 3.0L (4V) article. TEST the system for normal operation.
    2. 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.
  11. D11 CHECK CIRCUIT 321 (GY/WH) FOR A SHORT TO POWER 
    • Key in OFF position.
    • Disconnect: A/C Clutch Field Coil C100
    • Key in ON position.
      • Fig 3: Checking Circuit For Voltage
      GF0025642Courtesy of FORD MOTOR CO.
    • Measure the voltage between A/C clutch field coil C100-1, circuit 321 (GY/WH), harness side and ground.
    • Is the voltage greater than 10 volts? 
    1. YES  : REPAIR the circuit. TEST the system for normal operation.
    2. NO  : CHECK the clutch air gap. REFER to Air Conditioning (A/C) Clutch Air Gap Adjustment .
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