REFRIGERANT(for HFO-1234yf(R1234yf)) ON-VEHICLE INSPECTION

PROCEDURE

INSPECT REFRIGERANT PRESSURE

This method uses a refrigerant recovery unit set to locate problem areas. Read the refrigerant pressure when the test conditions are established.

Test conditions:

Temperature at the air inlet with the air recirculation switch set at RECIRC is 30 to 35°C (86 to 95°F).
Engine is running at 1500 rpm.
All doors are fully open.
Blower speed control switch is set to HI.
A/C switch is on.

Gauge readings (Reference):

Table 1. Text in Illustration
*a	Pressure on low-pressure side	*b	Blower HI Zone
*c	Blower LO Zone	*d	Pressure on high-pressure side

Normally functioning refrigeration system.

Gauge Reading


Pressure Side	Refrigerant Volume
Low	0.15 to 0.25 MPa (1.5 to 2.5 kgf/cm²)
High	1.37 to 1.57 MPa (14 to 16 kgf/cm²)

The A/C system periodically changes between normal and improper function due to moisture in the refrigerant system.

Table 2. Text in Illustration
*a	Low Pressure Side	*b	High Pressure Side


Symptom	Probable Cause	Diagnosis	Corrective Action
During operation, pressure on low pressure side cycles between normal and vacuum	Moisture in refrigeration system freezes at expansion valve orifice, causing temporary stop of cycle. However, when melted, normal state is restored.	Dryer is overly saturated Moisture in refrigeration system freezes at expansion valve orifice and blocks refrigerant circulation	Replace cooler dryer Remove moisture from cycle by repeatedly evacuating air Supply appropriate volume of new refrigerant

The A/C system does not function effectively due to insufficient refrigerant.

Table 3. Text in Illustration
*a	Low Pressure Side	*b	High Pressure Side


Symptom	Probable Cause	Diagnosis	Corrective Action
Pressure low on both low and high pressure sides Cooling performance insufficient	Gas leakage from refrigeration system	Insufficient refrigerant Refrigerant leakage	Check for gas leakage and repair if necessary Supply appropriate volume of new refrigerant If indicated pressure value close to 0 with gauge connected, create vacuum after inspecting and repairing location of leakage

The A/C system does not function effectively due to poor circulation of the refrigerant.

Table 4. Text in Illustration
*a	Low Pressure Side	*b	High Pressure Side


Symptom	Probable Cause	Diagnosis	Corrective Action
Pressure low on both low and high pressure sides Frost exists on piping from condenser to A/C unit	Refrigerant flow obstructed by dirt in condenser	Condenser clogged	Replace condenser

The A/C system does not function or functions intermittently because the refrigerant does not circulate.

Table 5. Text in Illustration
*a	Low Pressure Side	*b	High Pressure Side


Symptom	Probable Cause	Diagnosis	Corrective Action
Vacuum indicated on low pressure side, and extremely low pressure indicated on high pressure side Frost or condensation seen on piping on both sides of condenser or expansion valve	Refrigerant flow obstructed by moisture or dirt in refrigeration system Refrigerant flow obstructed by gas leakage from expansion valve	Refrigerant does not circulate	Check expansion valve refrigerant Clean expansion valve using compressed air Replace condenser Evacuate air and charge system with appropriate volume of new refrigerant For gas leakage from expansion valve, replace expansion valve

The A/C system does not function effectively due to the system being overcharged with refrigerant or insufficient cooling of the condenser.

Table 6. Text in Illustration
*a	Low Pressure Side	*b	High Pressure Side


Symptom	Probable Cause	Diagnosis	Corrective Action
Pressure extremely high on both low and high-pressure sides	Excessive refrigerant Cooling performance of condenser insufficient	Condenser is dirty Condenser fan motor is malfunctioning Excessive refrigerant	Clean condenser Check condenser fan motor operation If actions taken in 1 and 2 do not solve problem, check amount of refrigerant and adjust amount of refrigerant to appropriate amount

The A/C system does not function due to air in the refrigeration system.

CAUTION:

The low-pressure piping may be very hot and cause serious burns.

Note:

These gauge indications occur when the refrigeration system opens and the system is charged with refrigerant without vacuum purging.

Table 7. Text in Illustration
*a	Low Pressure Side	*b	High Pressure Side


Symptom	Probable Cause	Diagnosis	Corrective Action
Pressure extremely high on both low and high-pressure sides Low-pressure piping is too hot to touch	Air in refrigeration system	Air in refrigeration system Vacuum purging insufficient	Check if compressor oil is dirty or insufficient Evacuate air and charge system with new refrigerant

The A/C system does not function effectively due to an expansion valve malfunction.

Table 8. Text in Illustration
*a	Low Pressure Side	*b	High Pressure Side


Symptom	Probable Cause	Diagnosis	Corrective Action
Pressure extremely high on both low and high-pressure sides Frost or condensation on piping on low-pressure side	Problem with expansion valve	Excessive refrigerant in low pressure piping Expansion valve open too widely	Replace expansion valve

The A/C system does not function due to a defective compressor.

Table 9. Text in Illustration
*a	Low Pressure Side	*b	High Pressure Side


Symptom	Probable Cause	Diagnosis	Corrective Action
Pressure extremely high on both low and high-pressure sides Pressure extremely low on high pressure side	Internal leakage in compressor	Compression failure Leakage from damaged valve or broken sliding parts	Repair or replace compressor