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

WARNING: This page is about a different car, the 2010 Lincoln MKX and 2010 Ford Edge. 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, PCM or IC  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. L1 CHECK THE A/C PRESSURE SENSOR (ACP_PSI) PCM PID 
    • Ignition ON.
    • Enter the following diagnostic mode on the scan tool: ACP_PSI PCM PID.
    • With the manifold gauge set connected, compare the pressure readings of the manifold gauge set and the ACP_PSI PID.
    • Are the pressure values of the manifold gauge set and the ACP_PSI PID similar? 
    • Yes:  GO to L2  .
    • No:  INSTALL a new A/C pressure transducer. TEST the system for normal operation.
  2. L2 CHECK THE POST EVAPORATOR TEMPERATURE SENSOR INPUT (PEVAP_TMP) HVAC PID 
    • Allow the vehicle exterior and interior to stabilize to ambient temperature.
    • Enter the following diagnostic mode on the scan tool: PEVAP_TMP HVAC PID.
    • Does the PEVAP_TMP HVAC PID read similar to the ambient temperature? 
    • Yes:  For DATC  systems, GO to L3  .

      For EMTC  systems, GO to  L4.

    • No:  CARRY OUT the Evaporator Temperature Sensor component test. See Component Tests . If the sensor tests OK, GO to  L13. If the sensor does not test OK, INSTALL a new heater core and evaporator core housing. REFER to CLIMATE CONTROL . CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  3. L3 CHECK THE AIR CONDITIONING SWITCH STATUS (CC_AC) HVAC PID WITH THE A/C ON 
    • Enter the following diagnostic mode on the scan tool: CC_AC HVAC PID.
    • Press the PANEL and A/C manual override buttons on the HVAC module - DATC  .
    • Does the CC_AC HVAC PID read ON? 
    • Yes:  GO to  L5.
    • No:  GO to  L13.
  4. L4 CHECK THE HVAC MODULE - EMTC A/C SIGNAL WITH THE A/C ON 
    NOTE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the SPECIAL TOOL REFERENCE  table . To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test light probe directly on any connector.
    • Ignition OFF.
    • Disconnect: IC  C220.
    • Ignition ON.
    • Select PANEL mode and press the A/C button on the HVAC module - EMTC  .
    • Connect a 12-volt test light between IC  C220-23, circuit CH434 (GY/YE), harness side and IC  C220-19, circuit SBP26 (YE/RD), harness side.
      Fig 1: Connecting 12-Volt Test Light Between IC C220-23, Circuit CH434 (GY/YE) And IC C220-19, Circuit SBP26 (YE/RD)
      G06505327Courtesy of FORD MOTOR CO.
    • Does the test light illuminate? 
    • Yes:  GO to L5  .
    • No:  GO to  L7.
  5. L5 CHECK THE AIR CONDITIONING COMPRESSOR CYCLING SWITCH (ACCS) PCM PID WITH THE A/C ON 
    • Ignition OFF.
      • NOTE: EMTC  systems only.
    • Connect: EMTC Systems Only  , IC  C220.
    • Ignition ON.
      • NOTE: EMTC  systems only.
    • Enter the following diagnostic mode on the scan tool: ACCS PCM PID.
    • With the engine running, press the PANEL and A/C manual override buttons on the HVAC module - DATC  or select MAX A/C on the HVAC module - EMTC  .
    • Does the ACCS PCM PID read ON? 
    • Yes:  GO to L6  .
    • No:  GO to  L14.
  6. L6 CHECK THE AIR CONDITIONING CLUTCH (WAC/ACCR) PCM PID WITH THE A/C ON 
    • Enter the following diagnostic mode on the scan tool: WAC/ACCR PCM PID.
    • Does the WAC/ACCR PCM PID read ON? 
    • Yes:  GO to  L9.
    • No:  GO to  L14.
  7. L7 CHECK CIRCUIT CH434 (GY/YE) FOR AN OPEN 
    • Ignition OFF.
    • Disconnect: HVAC Module - EMTC  C2357A.
    • Measure the resistance between HVAC module - EMTC  C2357A-2, circuit CH434 (GY/YE), harness side and IC  C220-23, circuit CH434 (GY/YE), harness side.
      Fig 2: Measuring Resistance Between HVAC Module - EMTC C2357A-2, Circuit CH434 (GY/YE) And IC C220-23, Circuit CH434 (GY/YE)
      G06505328Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    • Yes:  GO to L8  .
    • No:  REPAIR circuit CH434 (GY/YE) for an open. TEST the system for normal operation.
  8. L8 CHECK CIRCUIT CH434 (GY/YE) FOR A SHORT TO VOLTAGE 
    • Ignition ON.
    • Measure the voltage between HVAC module - EMTC  C2357A-2, circuit CH434 (GY/YE), harness side and ground.
      Fig 3: Measuring Voltage Between HVAC Module - EMTC C2357A-2, Circuit CH434 (GY/YE), Harness Side And Ground
      G06505329Courtesy of FORD MOTOR CO.
    • Is any voltage present? 
    • Yes:  REPAIR circuit CH434 (GY/YE) for a short to voltage. TEST the system for normal operation.
    • No:  GO to  L14.
  9. L9 CHECK THE VOLTAGE AT THE A/C COMPRESSOR CLUTCH FIELD COIL 
    • Ignition OFF.
    • Disconnect: A/C Compressor Clutch Field Coil C100.
    • Ignition ON.
    • With the engine running, 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 CH401 (VT/WH), harness side and ground.
      Fig 4: Measuring Voltage Between A/C Compressor Clutch Field Coil C100-1, Circuit CH401 (VT/WH) And Ground
      G06505330Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes:  GO to L10  .
    • No:  CARRY OUT the A/C Control Relay component test.

      Refer to COMPONENT TESTING for component testing.

      If the relay tests OK, GO to  L11.

  10. L10 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 GD120 (BK/GN), harness side and ground.
      Fig 5: Measuring Resistance Between A/C Compressor Clutch Field Coil C100-2, Circuit GD120 (BK/GN), Harness Side And Ground
      G06505331Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    • Yes:  INSTALL a new A/C compressor. REFER to CLIMATE CONTROL . TEST the system for normal operation.
    • No:  REPAIR circuit GD120 (BK/GN) for an open. TEST the system for normal operation.
  11. L11 CHECK THE RELAY SWITCH FOR VOLTAGE 
    • Ignition OFF.
    • Disconnect: A/C Clutch Relay.
    • Ignition ON.
    • Measure the voltage between A/C clutch relay socket and ground.
      Fig 6: Measuring Voltage Between A/C Clutch Relay Socket And Ground
      G06505332Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes:  GO to L12  .
    • No:  VERIFY BJB  fuse 35 (10A) is OK. If OK, INSTALL a new BJB  . TEST the system for normal operation.
  12. L12 CHECK CIRCUIT CH401 (VT/WH) FOR AN OPEN 
    • Ignition OFF.
    • Measure the resistance between 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 7: Measuring Resistance Between A/C Clutch Relay Socket, Circuit CH401 (VT/WH) And A/C Compressor Clutch Field Coil C100-1, Circuit CH401 (VT/WH)
      G06505333Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 
    • Yes:  GO to  L14.
    • No:  REPAIR circuit CH401 (VT/WH) for an open. TEST the system for normal operation.
  13. L13 CHECK THE HVAC MODULE CONNECTION 
    • Inspect the HVAC module connectors for:
      • corrosion.
      • pushed-out terminals.
      • damaged terminals.
    • Connect and correctly seat all the HVAC module connectors.
    • Clear the DTCs.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 
    • Yes:  INSTALL a new HVAC 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.
  14. L14 CHECK THE PCM CONNECTION 
    • Disconnect all the PCM connectors.
    • Inspect the module connectors for:
      • corrosion.
      • pushed-out terminals.
      • damaged terminals.
    • Connect and correctly seat all the PCM connectors.
    • Clear the DTCs.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 
    • 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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