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

WARNING: This page is about a different car, the 2006 Ford Pickup, 2006 Ford F550 Super Duty, 2006 Ford F450 Super Duty, and 2006 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

K1 CHECK PID WACF WITH THE A/C OFF
- Key in ON position.
- Place the function selector switch to the OFF position or press the OFF manual override button on the EATC module.
- Enter the following diagnostic mode on the scan tool: PCM PID WACF.
- Does the PCM PID WACF read YES?
Yes : REPAIR circuit 331 (PK/YE) for a short to ground. TEST the system for normal operation.

No : GO to K2.
K2 CHECK PID ACCS WITH THE A/C OFF
- Enter the following diagnostic mode on the scan tool: PCM PID ACCS
- Does the PCM PID ACCS read ON?
Yes : GO to K3.

No : GO to K7.
K3 CHECK FOR VOLTAGE AT THE A/C CYCLING SWITCH
- Key in OFF position.
- Disconnect: A/C Cycling Switch C1081.
- Key in ON position.
- Measure the voltage between A/C cycling switch C1081-4, circuit 348 (VT) and ground.
  
  Fig 1: Measuring Voltage Between connector And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : GO to K4.

No : GO to K5.
K4 CHECK CIRCUIT 348 (VT) FOR A SHORT TO VOLTAGE
- Key in OFF position.
- Disconnect: Function Selector Switch C294a or EATC module C228b.
- Key in ON position.
- Measure the voltage between A/C cycling switch C1081-4, circuit 348 (VT) and ground.
  
  Fig 2: Measuring Voltage Between connector And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : REPAIR circuit 348 (VT) for a short to voltage. TEST the system for normal operation.

No : INSTALL a new function selector switch (manual A/C), or INSTALL a new EATC module (EATC). REFER to CLIMATE CONTROL . TEST the system for normal operation.
K5 CHECK CIRCUIT 441 (RD/YE) FOR A SHORT TO VOLTAGE
- Key in OFF position.
- Disconnect: A/C Pressure Cutoff Switch C1078.
- Key in ON position.
- Measure the voltage between A/C pressure cutoff switch C1078-1, circuit 441 (RD/YE) and ground.
  
  Fig 3: Checking Circuit 441 (RD/YE) For Short To Voltage
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : REPAIR circuit 441 (RD/YE) for a short to voltage. TEST the system for normal operation.

No : GO to K6.
K6 CHECK CIRCUIT 439 (TN/LG) FOR A SHORT TO VOLTAGE
- Measure the voltage between A/C pressure cutoff switch C1078-3, circuit 439 (TN/LG) and ground.
  
  Fig 4: Checking Circuit 439 (TN/LG) For Short To Voltage
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : REPAIR circuit 439 (TN/LG) for a short to voltage. TEST the system for normal operation.

No : INSTALL a new PCM. TEST the system for normal operation.
K7 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.
- Measure the voltage between A/C compressor clutch field coil C100-1, circuit 321 (GY/WH) and ground.
  
  Fig 5: 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 K8.

No : ADJUST the A/C compressor clutch air gap. REFER to AIR CONDITIONING (A/C) CLUTCH AIR GAP ADJUSTMENT . TEST the system for normal operation.
K8 CHECK CIRCUIT 321 (GY/WH) FOR A SHORT TO VOLTAGE
- Key in OFF position.
- Disconnect: A/C Control Relay.
- Key in ON position.
- Measure the voltage between A/C compressor clutch field coil C100-1, circuit 321 (GY/WH) and ground.
  
  Fig 6: Measuring Voltage Between A/C Compressor Clutch Field Coil And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : REPAIR circuit 321 (GY/WH) for a short to voltage. TEST the system for normal operation.

No : INSTALL a new A/C control relay. CHECK the A/C clutch diode. INSTALL a new diode, if necessary. TEST the system for normal operation.