Refrigerant System Tests
WARNING: This page is about a different car, the 2015 Lincoln MKC. However, it is still accessible from the selected car via links, so may be relevant.
Refrigerant System Tests
Inspection
NOTE:
In order to perform an accurate test the vehicle ambient temperature must be 21°C (70°F) or above.
- 1.NOTE: Procedure 1 - Ambient Temperature between 21°C (70°F) and 38°C (100°F)
Run the engine until it reaches normal operating temperature.
- 3.
Set temperature to (lowest possible temp 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 Air Conditioning (A/C) switch or compressor on switch, set it to Air Conditioning (A/C) ON.
- 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.
- 8.
Determine if the discharge pressure falls within the normal operating limits using theNormal Refrigerant Discharge Pressures 21 - 38°C (70 - 100°F) Ambient (30 - 60% Relative Humidity) chart below.
- 10.
Determine if the suction pressure falls within the normal operating limits using theNormal Refrigerant Suction Pressures 21 - 38°C (70 - 100°F) Ambient (30 - 60% Relative Humidity) chart below.
- 11.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 computerAdditional 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.NOTE: Procedure 2 - Ambient Temperature Above 38°C (100°F)
Run the engine until it reaches normal operating temperature.
- 3.
Set temperature to (lowest possible temp 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 Air Conditioning (A/C) switch or compressor on switch, set it to Air Conditioning (A/C) ON.
- 4.
Open all vehicle windows and leave the hood open for the test. Open the rear hatch and/or rear doors (if equipped).
- 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.
- 8.
Determine if the discharge pressure falls within the normal operating limits using theNormal Refrigerant Discharge Pressures 38 - 49°C (100 - 120°F) Ambient (15 - 40% Relative Humidity) chart below.
- 10.
Determine if the suction pressure falls within the normal operating limits using theNormal Refrigerant Suction Pressures 38 - 49°C (100 - 120°F) Ambient (15 - 40% Relative Humidity) chart below.
- 11.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 computerAdditional 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.