Pinpoint Test J: The Air Conditioning (A/C) Is Always On

WARNING: This page is about a different car, the 2006 Mercury Montego, 2006 Ford Freestyle, and 2006 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

Before carrying out the following test, diagnose any PCM or instrument cluster DTCs.
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.

Test Step

J1 CHECK THE A/C PRESSURE PCM PID
- Key in ON position.
- Enter the following diagnostic mode on the scan tool: A/C Pressure PCM PID.
- With the manifold gauge set connected, compare the pressure readings of the manifold gauge set and the A/C pressure PID.
- Are the pressure values of the manifold gauge set and the A/C pressure PID similar?
Yes: GO to J2.

No: INSTALL a new A/C pressure transducer. TEST the system for normal operation.
J2 CHECK THE A/C EVAPORATOR TEMPERATURE 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 scan tool: A/C Evaporator Discharge Temperature PCM PID.
- Does the A/C evaporator discharge temperature PID read similar to the ambient temperature?
Yes: GO to J3.

No: INSTALL a new A/C evaporator discharge temperature sensor. TEST the system for normal operation.
J3 CHECK A/C REQUEST PID WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: PCM A/C REQUEST PID.
- Does the PCM A/C REQUEST PID read ON?
Yes: EATC, GO to J4.

EMTC, GO to J5.

No: GO to J7.
J4 CHECK A/C SWITCH PID WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: PCM A/C SWITCH PID.
- Does the PCM A/C SWITCH PID read ON?
Yes: GO to J10.

No: GO to J11.
J5 CHECK EMTC A/C REQUEST OUTPUT
- Key in OFF position.
- Disconnect: IC C220.
- Key in ON position.
- Select the OFF position on the EMTC module.
- Measure the resistance between IC C220-10, circuit 1424 (TN/BK) and ground.
  
  Fig 1: Checking EMTC A/C Request Output
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes: GO to J6.

No: GO to J11.
J6 CHECK CIRCUIT 1424 (TN/BK) FOR A SHORT TO GROUND
- Key in OFF position.
- Disconnect: EMTC C294a.
- Key in ON position.
- Measure the resistance between IC C220-10, circuit 1424 (TN/BK) and ground.
  
  Fig 2: Checking Circuit 1424 (TN/BK) For Short To Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10,000 ohms?
Yes: GO to J10.

No: REPAIR circuit 1424 (TN/BK) for a short to ground. TEST the system for normal operation.
J7 CHECK A/C CLUTCH RELAY PID WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: PCM A/C CLUTCH RELAY PID.
- Does the PCM A/C CLUTCH RELAY PID read ON?
Yes: REFER to INTRODUCTION - GASOLINE article.

No: GO to J8.
J8 CHECK FOR VOLTAGE TO THE A/C COMPRESSOR CLUTCH FIELD COIL
- Key in OFF position.
- Disconnect: A/C Compressor Clutch Field Coil C100.
- Key in ON position.
- Select the OFF position on the EMTC module.
- Measure the voltage between A/C compressor clutch field coil C100-1, circuit 1810 (LG/OG) and ground.
  
  Fig 3: Checking For Voltage To A/C Compressor Clutch Field Coil
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes: GO to J9.

No: ADJUST the A/C compressor clutch gap. refer to AIR CONDITIONING (A/C) CLUTCH AIR GAP ADJUSTMENT . TEST the system for normal operation.
J9 CHECK CIRCUIT 1810 (LG/OG) FOR A SHORT TO VOLTAGE
- Key in OFF position.
- Disconnect: A/C Clutch Relay.
- Key in ON position.
- Measure the voltage between A/C compressor clutch field coil C100-1, circuit 1810 (LG/OG) and ground.
  
  Fig 4: Checking Circuit 1810 (LG/OG) For Short To Voltage
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes: REPAIR circuit 1810 (LG/OG) for a short to voltage. TEST the system for normal operation.

No: INSTALL a new A/C clutch relay. Check the A/C clutch diode. INSTALL a new diode if necessary. TEST the system for normal operation.
J10 CHECK MODULE CONNECTION
- Carry out the Electronic Automatic Temperature Control (EATC) Module and Electronic Manual Temperature Control (EMTC) Module Cold Boot Process.
- Carry out the EATC on-demand self test.
- Operate the system.
- Does the concern return?
Yes: INSTALL a new EATC or EMTC 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.
J11 CHECK PCM MODULE 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?
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.