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

WARNING: This page is about a different car, the 2008 Mercury Sable, 2008 Ford Taurus X, and 2008 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: It is important to install relays in their correct position in the Battery Junction Box (BJB)). Installing a relay incorrectly may cause wiring shorts or damage to modules. While carrying out diagnostics on relays, have only one BJB relay removed at a time. Failure to follow these instructions may result in damage to the vehicle circuitry or to control modules.
NOTE: Some PCM DTCs may inhibit A/C operation. If any PCM DTCs are retrieved, diagnose those first. Refer to the PCM DTC Table .
NOTE: Before carrying out the following test, diagnose any Instrument Cluster (IC) DTCs.
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.
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. K1 CHECK THE A/C PRESSURE SENSOR (ACP_PRESS) PCM PID 
    • Key in ON position.
    • Enter the following diagnostic mode on the diagnostic tool: ACP_PRESS PCM PID
    • With the R-134a Manifold Gauge Set connected, compare the pressure readings of the R-134a Manifold Gauge Set and the ACP_PRESS PID.
    • Are the pressure values of the R-134a Manifold Gauge Set and the ACP_PRESS PID similar? 
    1. YES  : Go to  K2.
    2. NO  : INSTALL a new A/C pressure transducer. TEST the system for normal operation.
  2. K2 CHECK THE AIR CONDITIONING SWITCH STATUS (AC_SEL_SW) HVAC PID WITH THE A/C ON 
    • Enter the following diagnostic mode on the diagnostic tool: AC_SEL_SW HVAC PID
    • Press the PANEL manual override button and press the A/C button (indicator on) on the HVAC module - DATC or select PANEL mode and press the A/C button (indicator on) on the HVAC module - EMTC.
    • Does the AC_SEL_SW HVAC PID read PRESSED? 
    1. YES  : DATC, go to  K3.

      EMTC, CARRY OUT the A/C Evaporator Discharge Temperature Sensor Component Test. If the sensor tests OK, go to  K4.

    2. NO  : Go to  K10.
  3. K3 CHECK THE A/C EVAPORATOR TEMPERATURE (EVAP_TEMP) HVAC ) 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 diagnostic tool: EVAP_TEMP HVAC PID
    • Does the EVAP_TEMP HVAC PID read similar to the ambient temperature? 
    1. YES  : Go to  K4.
    2. NO  : INSTALL a new A/C evaporator discharge temperature sensor. TEST the system for normal operation.
  4. K4 CHECK THE AIR CONDITIONING CLUTCH (WAC/ACCR) PCM PID WITH THE A/C ON 
    • Enter the following diagnostic mode on the diagnostic tool: WAC/ACCR PCM PID
    • Does the WAC/ACCR PCM PID read ON? 
    1. YES  : Go to  K5.
    2. NO  : Go to  K11.
  5. K5 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL 
    • Key in OFF position.
    • Disconnect: A/C Compressor Clutch Field Coil C100
    • Key in ON position.
    • Press the PANEL and A/C manual override buttons on the HVAC module - DATC or select MAX A/C on the HVAC module - EMTC.
    • Measure the voltage between A/C compressor clutch field coil C100-1, circuit CH421 (GY), harness side and ground.
      • Fig 1: Measuring Voltage
      G04002936Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    1. YES  : Go to  K6.
    2. NO  : Go to  K8.
  6. K6 CHECK THE GROUND AT THE A/C COMPRESSOR CLUTCH FIELD COIL 
    • Key in OFF position.
    • Measure the resistance between A/C compressor clutch field coil C100-2, circuit GD120 (BK/GN), harness side and ground.
      • Fig 2: Checking Circuit
      GF0004337Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  K7.
    2. NO  : REPAIR circuit GD120 (BK/GN) for an open. TEST the system for normal operation.
  7. K7 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 3: Checking A/C Compressor Clutch Air Gap
      GF0004342Courtesy of FORD MOTOR CO.
    • Is the A/C compressor clutch air gap average greater than 0.65 mm (0.030 in)? 
    1. YES  : ADJUST the A/C compressor clutch gap. REFER to Air Conditioning (A/C) Clutch Air Gap Adjustment . TEST the system for normal operation.
    2. NO  : INSTALL a new A/C compressor clutch field coil. TEST the system for normal operation.
  8. K8 CHECK THE A/C CLUTCH RELAY FOR VOLTAGE 
    • Key in OFF position.
    • Disconnect: A/C Clutch Relay
    • Key in ON position.
    • Measure the voltage between the A/C clutch relay socket, circuit SBB24 (VT/RD) and ground.
      • Fig 4: Measuring Voltage
      GF0045989Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    1. YES  : Go to  K9.
    2. NO  : VERIFY Battery Junction Box (BJB) fuse 24 (10A) is OK. If OK, REPAIR circuit SBB24 (VT/RD) for an open. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams Manual to identify the possible causes of the circuit short.
  9. K9 CHECK CIRCUIT CH421 (GY) FOR AN OPEN 
    • Key in OFF position.
    • Measure the resistance between the A/C clutch relay socket, circuit CH421 (GY) and A/C compressor clutch field coil C100-1, circuit CH421 (GY), harness side.
      • Fig 5: Measuring Resistance
      GF0045990Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    1. YES  : CARRY OUT the A/C clutch relay component test. If the relay tests OK, go to  K11.
    2. NO  : REPAIR circuit CH421 (GY) for an open. TEST the system for normal operation.
  10. K10 CHECK THE MODULE CONNECTION 
    • Carry out the HVAC Module Cold Boot Process.
      • NOTE: DATC systems only.
    • Carry out the HVAC Module - Dual Automatic Temperature Control (DATC) On-Demand Self Test.
    • Operate the system.
    • Does the concern return? 
    1. YES  : INSTALL a new HVAC module. REFER to CLIMATE CONTROL 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. TEST the system for normal operation.
  11. K11 CHECK THE PCM CONNECTION 
    • Clear the DTCs.
    • Disconnect all of the PCM connectors.
    • Check for:
      • corrosion.
      • pushed-out connectors.
      • incorrectly seated connector.
    • Connect and correctly seat all of the PCM connectors.
    • Operate the system.
    • Does the concern return? 
    1. YES  : INSTALL a new PCM. 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.
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