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Pinpoint Test O: The Air Conditioning (A/C) Is Inoperative

WARNING: This page is about a different car, the 2014 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Before carrying out the following test, diagnose any HVAC or PCM DTCs.
NOTE: Before carrying out the following test, check that the A/C system pressure is above 290 kPa (42 psi). If the pressure is below 290 kPa (42 psi), refer to FLUORESCENT DYE LEAK DETECTION .
  1. O1 CHECK THE A/C SYSTEM PRESSURE 
    • Ignition OFF.
    • With the R-134a manifold gauge set connected, check the A/C system pressure.

    Is the A/C system pressure above 290 kPa (42 psi)? 

  2. O2 CHECK THE A/C PRESSURE SENSOR (ACP_PRESS) PCM PID 
    • Ignition ON.
    • Enter the following diagnostic mode on the scan tool: PCM Data Logger.
    • With the R-134a manifold gauge set connected, compare the pressure readings of the manifold gauge set and the ACP_PRESS PCM PID.

    Are the pressure values of the manifold gauge set and the ACP_PRESS PID similar? 

    • Yes  : GO to O3  .
    • No  : INSTALL a new A/C pressure transducer. TEST the system for normal operation.
  3. O3 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) HVAC PID 
    • Allow the vehicle exterior and interior to stabilize to the ambient temperature.
    • Enter the following diagnostic mode on the scan tool: HVAC Data Logger.
    • Monitor the EVAP_TEMP HVAC PID

    Does the EVAP_TEMP HVAC PID read similar to the ambient temperature? 

  4. O4 CHECK THE AC_DEMAND HVAC PID WITH THE A/C ON 
    • Enter the following diagnostic mode on the scan tool: HVAC Data Logger.
    • Select PANEL press the A/C button (indicator on) on the HVAC controls and monitor the AC_DEMAND HVAC PID.

    Does the AC_DEMAND HVAC PID read Active? 

    • Yes  : GO to O5  .
    • No  : GO to  O17.
  5. O5 CHECK THE (A/C) SWITCH (CC_SW_AC) FCIM PID WITH THE A/C ON 
    • Enter the following diagnostic mode on the scan tool: FCIM  Data Logger.
    • Select PANEL press the A/C button (indicator on) on the HVAC controls and monitor the CC_SW_AC FCIM  PID.

    Does the CC_SW_AC FCIM PID read Active? 

    • Yes  : GO to O6  .
    • No  : INSTALL a new Front Controls Interface Module (FCIM). Refer to the appropriate article for the procedure. TEST the system for normal operation.
  6. O6 CHECK THE AIR CONDITIONING REQUEST SIGNAL (AC_REQ) PCM PID WITH THE A/C ON 
    • Enter the following diagnostic mode on the scan tool: PCM Data Logger.
    • Select PANEL press the A/C button (indicator on) on the HVAC controls and monitor the AC_REQ PCM PID.

    Does the AC_REQ PCM PID read YES? 

    • Yes  : GO to O7  .
    • No  : GO to  O17.
  7. O7 CHECK THE AIR CONDITIONING COMPRESSOR COMMANDED STATE (ACC_CMD) PCM PID WITH THE A/C ON 
    • Enter the following diagnostic mode on the scan tool: PCM Data Logger.
    • Select PANEL press the A/C button (indicator on) on the HVAC controls and monitor the ACC_CMD PCM PID.

    Does the ACC_CMD PCM PID read ON? 

    • Yes  : GO to O8  .
    • No  : GO to  O18.
  8. O8 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY COIL 
    • Ignition OFF.
    • Disconnect: A/C Clutch Relay.
    • Ignition ON.
    • Measure the voltage between ground and the A/C clutch relay socket, circuit CBB77 (WH).
      Fig 1: Measuring Voltage Between A/C Clutch Relay Socket And Ground
      G06133019Courtesy of FORD MOTOR CO.

    Is the voltage greater than 11 volts? 

    • Yes  : GO to O9  .
    • No  : VERIFY Battery Junction Box (BJB) fuse 77 (10A) is OK. If OK, REPAIR circuit CBB77 (WH) for an open. TEST the system for normal operation. If not OK, REFER to the OEM WIRING DIAGRAMS to identify the possible causes of the circuit short.
  9. O9 CHECK THE A/C CLUTCH RELAY 
    • Start the engine.
    • Select PANEL and press the A/C button (indicator on) on the HVAC controls.
    • With the engine running, connect a 12-volt test light between A/C clutch relay socket, circuit CBB77 (WH) and A/C clutch relay socket, circuit CH302 (WH/BN).
      Fig 2: Checking A/C Clutch Relay
      G07963797Courtesy of FORD MOTOR CO.

    Does the test light illuminate? 

    • Yes  : GO to  O12.
    • No  : GO to O10  .
  10. O10 CHECK THE A/C CLUTCH RELAY COIL SWITCHED GROUND CIRCUIT FOR A SHORT TO VOLTAGE 
    • Ignition OFF.
    • Disconnect: PCM C1381B (5.0L, 6.2L).
    • Disconnect: PCM C175B (3.7L).
    • Disconnect: PCM C1551B (3.5L).
    • Ignition ON.
    • For 3.7L, 5.0L and 6.2L 
      Fig 3: Measuring Voltage Between Ground And PCM C175B-12, Circuit CH302
      G06098542Courtesy of FORD MOTOR CO.

      Measure the voltage between ground and:

      • For 3.7L, PCM C175B-12  , circuit CH302 (WH/BN), harness side.
      • For 5.0L and 6.2L, PCM C1381B-12  , circuit CH302 (WH/BN), harness side.
    • For 3.5L 
      Fig 4: Measuring Voltage Between Ground And PCM C1551B-2, Circuit CH302
      G07412906Courtesy of FORD MOTOR CO.

      For 3.5L, measure the voltage between ground and PCM C1551B-2  , circuit CH302 (WH/BN), harness side.

    Is any voltage present? 

    • Yes  : REPAIR the circuit.
    • No  : GO to O11  .
  11. O11 CHECK THE A/C CLUTCH RELAY COIL SWITCHED GROUND CIRCUIT FOR AN OPEN 
    • Ignition OFF.
    • For 3.7L, 5.0L and 6.2L 
      Fig 5: Checking A/C Clutch Relay Coil Switched Ground Circuit For Open
      G07412909Courtesy of FORD MOTOR CO.

      Measure the resistance between A/C clutch relay socket, circuit CH302 (WH/BN) and:

      • For 3.7L, PCM C175B-12  , circuit CH302 (WH/BN), harness side.
      • For 5.0L and 6.2L, PCM C1381B-12  , circuit CH302 (WH/BN), harness side.
    • For 3.5L 
      Fig 6: Measuring Resistance Between A/C Clutch Relay Socket And PCM C1551B-2, Circuit CH302
      G07412910Courtesy of FORD MOTOR CO.

      For 3.5L, measure the resistance between A/C clutch relay socket, circuit CH302 (WH/BN) and PCM C1551B-2  , circuit CH302 (WH/BN), harness side.

    Is the resistance less than 3 ohms? 

    • Yes  : GO to  O18.
    • No  : REPAIR the circuit.
  12. O12 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY SWITCH CONTACTS 
    • Measure the voltage between the A/C clutch relay socket, circuit SBB30 (BN/RD) and ground.
      Fig 7: Measuring Voltage Between A/C Clutch Relay Socket And Ground
      G06133070Courtesy of FORD MOTOR CO.

    Is the voltage greater than 11 volts? 

    • Yes  : GO to O13  .
    • No  : VERIFY Battery Junction Box (BJB) fuse 30 (10A) is OK. If OK, REPAIR circuit SBB30 (BN/RD) for an open. TEST the system for normal operation. If not OK, REFER to the OEM WIRING DIAGRAMS to identify the possible causes of the circuit short.
  13. O13 CHECK THE A/C COMPRESSOR CLUTCH FIELD COIL VOLTAGE CIRCUIT FOR AN OPEN 
    • Ignition OFF.
    • Disconnect: A/C Compressor Clutch Field Coil C100.
    • Measure the resistance between the A/C clutch relay socket, circuit CH401 (VT/WH) and A/C compressor clutch field coil C100-1  , circuit CH401 (VT/WH), harness side.
      Fig 8: Measuring Resistance Between A/C Clutch Relay Socket And A/C Compressor Clutch Field Coil C100-1, Circuit CH401
      G06141382Courtesy of FORD MOTOR CO.

    Is the resistance less than 3 ohms? 

    • Yes  : GO to O14  .
    • No  : REPAIR the circuit.
  14. O14 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL 
    • Connect: A/C Clutch Relay.
    • Ignition ON.
    • Select PANEL and press the A/C button (indicator on) on the HVAC controls.
    • Measure the voltage between A/C compressor clutch field coil C100-1  , circuit CH401 (VT/WH), harness side and ground.
      Fig 9: Measuring Voltage Between A/C Compressor Clutch Field Coil C100-1, Circuit CH401 And Ground
      G06064573Courtesy of FORD MOTOR CO.

    Is the voltage greater than 11 volts? 

    • Yes  : GO to O15  .
    • No  : INSTALL a new A/C clutch relay. TEST the system for normal operation.
  15. O15 CHECK THE GROUND AT THE A/C COMPRESSOR CLUTCH FIELD COIL 
    • Ignition OFF.
    • Measure the resistance between A/C compressor clutch field coil C100-2  , circuit GD123 (BK/GY), harness side and ground.
      Fig 10: Measuring Resistance Between A/C Compressor Clutch Field Coil C100-2, Circuit GD123 And Ground
      G06098588Courtesy of FORD MOTOR CO.

    Is the resistance less than 3 ohms? 

    • Yes  : GO to O16  .
    • No  : REPAIR the circuit.
  16. O16 CHECK THE A/C COMPRESSOR CLUTCH AIR GAP 
    • Measure the A/C compressor clutch air gap at 3 equally spaced locations between the clutch hub and the A/C compressor clutch pulley.
      Fig 11: Checking A/C Clutch Air Gap At Equally Spaced Places Between Clutch Plate And A/C Clutch Pulley
      G06064575Courtesy of FORD MOTOR CO.

    Is the A/C compressor clutch air gap average greater than 0.65 mm (0.026 in)? 

  17. O17 CHECK FOR CORRECT HVAC MODULE OPERATION 
    • Ignition OFF.
    • Disconnect and inspect all HVAC module connectors.
    • Repair:
      • corrosion (install new connector or terminals - clean module pins)
      • damaged or bent pins - install new terminals/pins
      • pushed-out pins - install new pins as necessary
    • Connect all HVAC module connectors. Make sure they seat and latch correctly.
    • Clear the DTCs.
    • Enter the following diagnostic mode on the scan tool: Self-Test - HVAC Module.
    • Operate the system and verify the concern is still present.

    Is the concern still present? 

    • Yes  : CHECK OASIS  for any applicable TSBs  . If a TSB  exists for this concern, DISCONTINUE this test and FOLLOW TSB  instructions. If no TSB  addresses this concern, INSTALL a new HVAC module. REFER to HEATING VENTILATION AIR CONDITIONING (HVAC) MODULE .
    • No  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.
  18. O18 CHECK FOR CORRECT PCM OPERATION 
    • Ignition OFF.
    • Disconnect and inspect all the PCM connectors.
    • Repair:
      • corrosion (install new connector or terminals - clean module pins)
      • damaged or bent pins - install new terminals/pins
      • pushed-out pins - install new pins as necessary
    • Connect all PCM connectors. Make sure they seat and latch correctly.
    • Operate the system and verify the concern is still present.
    • Connect and correctly seat all the PCM connectors.
    • Clear the DTCs.
    • Enter the following diagnostic mode on the scan tool: Self-Test - PCM.
    • Operate the system and verify the concern is still present.

    Is the concern still present? 

    • Yes  : CHECK OASIS  for any applicable TSBs  . If a TSB  exists for this concern, DISCONTINUE this test and FOLLOW TSB  instructions. If no TSB  addresses this concern, INSTALL a new PCM. REFER to POWERTRAIN CONTROL MODULE (PCM) .
    • No  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.
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