Refrigerant System Tests

Inspection 

1. 1.
   
   
   NOTE: Procedure 1 - Ambient Temperature below 21 °C (70 °F)
   NOTE: Variable compressors need to see a thermal load on the system in order to create normal operating pressures.
   NOTE: In order to perform an accurate test the vehicle ambient temperature must be 21 °C (70 °F) or above. Perform the follow steps to achieve normal operating pressures.

   Drive the vehicle or run the engine until it reaches normal operating temperature.

1. 2.
   
   Set temperature to the highest possible temperature setting with the dual function disabled (if equipped). Manually set blower on HI. If the vehicle has a fresh air/recirc button, set it to recirculation. If the vehicle has an A/C switch or compressor on switch, set it to A/C OFF.

1. 3.
   
   Close all vehicle windows and doors.

1. 4.
   
   Allow the vehicle to idle for 5 minutes.

1. 5.
   
   Confirm the cabin temp is above 24 °C (75 °F). Set the A/C switch or compressor on switch, to MAX A/C ON.

1. 6.
   
   Allow the vehicle to idle for 5 minutes.

1. 7.
   
   Turn engine off, and proceed to procedure 2 - ambient temperature between 21 °C (70 °F) and 38 °C (100 °F).

Inspection 

1. 1.
   
   
   NOTE: Procedure 2 - Ambient Temperature between 21 °C (70 °F) and 38 °C (100 °F)

   Run the engine until it reaches normal operating temperature.

1. 2.
   
   Connect the air conditioning service unit to the refrigerant system.

1. 3.
   
   Set temperature to the lowest possible temperature setting with the dual function disabled (if equipped). Manually set blower on HI. If the vehicle has a fresh air/recirc button, set it to FRESH. If the vehicle has an A/C switch or compressor on switch, set it to A/C ON.

1. 4.
   
   Open all vehicle windows and leave the hood open for the test. Open the rear doors.

1. 5.
   
   Confirm the compressor is operating and the engine cooling fan(s) are operating or engaged. Allow the vehicle to idle until the suction (low-side) and discharge (high-side) pressures are stable or fluctuate in a range that repeats.

1. 6.
   
   Record the ambient (shop) temperature.

1. 7.
   
   Record the discharge pressure. If the pressure is fluctuating, record the average value.

1. 8.
   
   Vehicles Without Rear 

   A/C

   System  , determine if the discharge pressure falls within the normal operating limits using the

   Normal Refrigerant Discharge Pressures 21 - 38 ° C (70 - 100 ° F) Ambient (30 - 60% Relative Humidity)  chart below.

Courtesy of FORD MOTOR COMPANY

1. 9.
   
   Vehicles With Rear 

   A/C

   System  , determine if the discharge pressure falls within the normal operating limits using the

   Normal Refrigerant Discharge Pressures 21 - 38 ° C (70 - 100 ° F) Ambient (30 - 60% Relative Humidity)  chart below.

Courtesy of FORD MOTOR COMPANY

1. 10.
   
   Record the suction pressure. If the pressure is fluctuating, record the average value.

1. 11.
   
   Vehicles Without Rear 

   A/C

   System  , determine if the suction pressure falls within the normal operating limits using the

   Normal Refrigerant Suction Pressures 21 - 38 ° C (70 - 100 ° F) Ambient (30 - 60% Relative Humidity)  chart below.

Courtesy of FORD MOTOR COMPANY

1. 12.
   
   Vehicles With Rear 

   A/C

   System  , determine if the suction pressure falls within the normal operating limits using the

   Normal Refrigerant Suction Pressures 21 - 38 ° C (70 - 100 ° F) Ambient (30 - 60% Relative Humidity)  chart below.

Courtesy of FORD MOTOR COMPANY

1. 13.
   
   
   NOTE: Use the following table to guide diagnosis of the refrigerant system if operating pressures are outside normal limits.

   Refer to the chart below.

   High (Discharge) Pressure	Low (Suction) Pressure	Component - Causes
   High	Normal to High	Condenser - inadequate airflow. Engine - overheating.
   Normal to High	Normal	Refrigerant overcharge - air in refrigerant.
   Normal to Low	High	A/C Compressor - low performance.
   Normal to Low	Normal to High	A/C suction line - partially restricted or plugged. (1)
   Normal to Low	Low	Low refrigerant charge - leak in system. A/C suction line - partially restricted or plugged. (2)
   Erratic Operation or Compressor Not Running		Ambient Air Temperature (AAT) sensor - poor connection. A/C pressure transducer - poor connection. Evaporator temperature sensor - poor connection. Low refrigerant charge - leak in system.
   Additional Possible Components or Causes Associated With Inadequate Compressor Operation
   Compressor drive belt - loose Compressor clutch - slipping Clutch coil open - shorted, or loose mounting Control assembly switch - dirty contacts or sticking open Clutch wiring circuit - high resistance, open or blown fuse Compressor operation interrupted by engine computer
   Additional Possible Components or Causes Associated With a Damaged Compressor
   Incorrect clutch air-gap Suction accumulator - refrigerant oil bleed hose plugged Refrigerant leaks
   (1) Low pressure reading will be normal to high if restriction is downstream of service access valve. (2) Low pressure reading will be low if restriction is upstream of service access valve.

Inspection 

1. 1.
   
   
   NOTE: Procedure 3 - Ambient Temperature Above 38 °C (100 °F)

   Run the engine until it reaches normal operating temperature.

1. 2.
   
   Connect the air conditioning service unit to the refrigerant system.

1. 3.
   
   Set temperature to the lowest possible temperature setting with the dual function disabled (if equipped). Manually set blower on HI. If the vehicle has a fresh air/recirc button, set it to FRESH. If the vehicle has an A/C switch or compressor on switch, set it to A/C ON.

1. 4.
   
   Open all vehicle windows and leave the hood open for the test. Open the rear hatch and/or rear doors (if equipped).

1. 5.
   
   Confirm the compressor is operating and the engine cooling fan(s) are operating or engaged. Allow the vehicle to idle until the suction (low-side) and discharge (high-side) pressures are stable or fluctuate in a range that repeats.

1. 6.
   
   Record the ambient (shop) temperature.

1. 7.
   
   Record the discharge pressure. If the pressure is fluctuating, record the average value.

1. 8.
   
   Vehicles Without Rear 

   A/C

   System  , determine if the discharge pressure falls within the normal operating limits using the

   Normal Refrigerant Discharge Pressures 38 - 49 ° C (100 - 120 ° F) Ambient (15 - 40% Relative Humidity)  chart below.

Courtesy of FORD MOTOR COMPANY

1. 9.
   
   Vehicles With Rear 

   A/C

   System  , determine if the discharge pressure falls within the normal operating limits using the

   Normal Refrigerant Discharge Pressures 38 - 49 ° C (100 - 120 ° F) Ambient (15 - 40% Relative Humidity)  chart below.

Courtesy of FORD MOTOR COMPANY

1. 10.
   
   Record the suction pressure. If the pressure is fluctuating, record the average value.

1. 11.
   
   Vehicles Without Rear 

   A/C

   System  , determine if the suction pressure falls within the normal operating limits using the

   Normal Refrigerant Suction Pressures 38 - 49 ° C (100 - 120 ° F) Ambient (15 - 40% Relative Humidity)  chart below.

Courtesy of FORD MOTOR COMPANY

1. 12.
   
   Vehicles With Rear 

   A/C

   System  , determine if the suction pressure falls within the normal operating limits using the

   Normal Refrigerant Suction Pressures 38 - 49 ° C (100 - 120 ° F) Ambient (15 - 40% Relative Humidity)  chart below.

Courtesy of FORD MOTOR COMPANY

1. 13.
   
   
   NOTE: Use the following table to guide diagnosis of the refrigerant system if operating pressures are outside normal limits.

   Refer to the chart below.

   High (Discharge) Pressure	Low (Suction) Pressure	Component - Causes
   High	Normal to High	Condenser - inadequate airflow. Engine - overheating.
   Normal to High	Normal	Refrigerant overcharge - air in refrigerant.
   Normal to Low	High	A/C Compressor - low performance.
   Normal to Low	Normal to High	A/C suction line - partially restricted or plugged. (1)
   Normal to Low	Low	Low refrigerant charge - leak in system. A/C suction line - partially restricted or plugged. (2)
   Erratic Operation or Compressor Not Running		Ambient Air Temperature (AAT) sensor - poor connection. A/C pressure transducer - poor connection. Evaporator temperature sensor - poor connection. Low refrigerant charge - leak in system.
   Additional Possible Components or Causes Associated With Inadequate Compressor Operation
   Compressor drive belt - loose Compressor clutch - slipping Clutch coil open - shorted, or loose mounting Control assembly switch - dirty contacts or sticking open Clutch wiring circuit - high resistance, open or blown fuse Compressor operation interrupted by engine computer
   Additional Possible Components or Causes Associated With a Damaged Compressor
   Incorrect clutch air-gap Suction accumulator - refrigerant oil bleed hose plugged Refrigerant leaks
   (1) Low pressure reading will be normal to high if restriction is downstream of service access valve. (2) Low pressure reading will be low if restriction is upstream of service access valve.