Refrigerant System Tests

Inspection

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: To perform an accurate test make sure the vehicle ambient temperature is 21°C (70°F) or above. Perform the following steps to achieve normal operating pressures.

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

2.

Set the A/C system temperature to the highest possible temperature setting with the dual function disabled (if equipped). Manually set the 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.

3.

Close all the vehicle windows and doors.

4.

Allow the vehicle to idle for 5 minutes.

5.

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

6.

Allow the vehicle to idle for 5 minutes.

7.

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

Inspection

NOTE: To perform an accurate test make sure the vehicle ambient temperature is 21°C (70°F) or above. Perform the following steps to achieve normal operating pressures.

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.

2.

Connect the air conditioning service unit to the refrigerant system.

3.

Set the A/C system 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.

4.

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

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.

6.

Record the ambient (shop) temperature.

7.

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

8.

For vehicles without a 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

9.

Vehicles with a 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

10.

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

11.

For 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

12.

For vehicles with a 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

13.

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

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.

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

Run the engine until it reaches normal operating temperature.

2.

Connect the air conditioning service unit to the refrigerant system.

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.

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.

6.

Record the ambient (shop) temperature.

7.

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

8.

For vehicles without a 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

9.

For vehicles with a 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

10.

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

11.

For vehicles without a 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

12.

For vehicles with a 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

13.

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

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

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.