REFRIGERANT

INSPECT REFRIGERANT VOLUME

Check the sight glass on the air conditioning tube and accessory.

Prepare the vehicle according to the chart below.

Compare the sight glass to the following chart.

Item	Symptom	Amount of refrigerant	Corrective Actions
1	Bubbles exist	Insufficient*	Check for gas leakage and repair if necessary Recharge with proper amount of refrigerant
2	No bubbles exist (DTC 76 is output)	Empty, insufficient, or excessive	Refer to 3 and 4
3	No temperature difference between compressor inlet and outlet	Empty or nearly empty	Check for gas leakage and repair if necessary Evacuate the AC system and recharge with proper amount of refrigerant
4	Considerable temperature difference between compressor inlet and outlet	Proper or excessive	Refer to 5 and 6
5	Immediately after air conditioning is turned off, refrigerant remains clear	Excessive	Recover refrigerant Evacuate the AC system and recharge with proper amount of refrigerant
6	Immediately after air conditioning is turned off, refrigerant foams and then becomes clear	Proper	-

*: Bubbles in the sight glass with the vehicle's interior temperature above 35°C (95°F) can be considered normal if cooling is sufficient.

INSPECT REFRIGERANT PRESSURE WITH MANIFOLD GAUGE SET

Tip:

This is a method where a manifold gauge set is used to help locate the problem.

Read the manifold gauge pressure when the following conditions are met:

Test conditions:

Temperature at the air inlet with the switch set at RECIRC is 30 to 35°C (86 to 95°F).
The engine is running at 1500 rpm.
The blower speed control switch position is at "HI".
The temperature control dial position is at "COOL".
The A/C switch is on.
Doors are fully open.
The ignition switch is in a position that enables the A/C compressor to run.

Normally functioning refrigeration system

Table 1. Gauge reading
Pressure side	Refrigerant volume
Low	0.15 to 0.25 MPa (1.5 to 2.5 kgf/cm², 21.3 to 35.5 psi)
High	1.37 to 1.57 MPa (14 to 16 kgf/cm², 199.1 to 227.5 psi)

Moisture is present in the refrigeration system.

Symptom	Probable Cause	Diagnosis	Corrective Actions
During operation, pressure on low pressure side cycles between normal and vacuum	Moisture in the AC system will freeze at the expansion valve orifice, causing the refrigeration cycle to temporarily stop After the system stops, and warms up again, the ice will melt and normal operation will be temporarily restored	Cooler dryer (integrated into condenser tank) in oversaturated state Moisture in refrigeration system freezes at expansion valve orifice and blocks circulation of refrigerant	Replace cooler dryer Remove moisture in system by repeatedly evacuating air Supply a proper amount of new refrigerant

Insufficient cooling

Symptom	Probable Cause	Diagnosis	Corrective Actions
Pressure is low on both low and high pressure sides Bubbles are seen through sight glass continuously Insufficient cooling performance	Gas leakage from the refrigeration system	Insufficient refrigerant Refrigerant leaking	Check for gas leaks and repair if necessary Supply a proper amount of new refrigerant If the gauge indicates a pressure of close to 0, then it will be necessary to evacuate the system after repairing the leak

Poor circulation of refrigerant

Symptom	Probable Cause	Diagnosis	Corrective Actions
Pressure is low on both low and high pressure sides Frost exists on pipe from condenser to unit	Refrigerant flow is obstructed by dirt inside the pipes of the condenser core	Receiver is clogged	Replace condenser

Refrigerant does not circulate.

Symptom	Probable Cause	Diagnosis	Corrective Actions
Vacuum is indicated on low pressure side and very low pressure is indicated on high pressure side Frost or condensation is seen on piping on both sides of receiver/drier or expansion valve	Refrigerant flow is obstructed by moisture or dirt in refrigeration system Refrigerant flow is disrupted by gas leaking internally through the expansion valve	Refrigerant does not circulate	Check expansion valve Replace expansion valve Replace condenser Evacuate air and supply a proper amount of new refrigerant For internal gas leak at expansion valve, replace expansion valve

Refrigerant is overcharged or cooling effectiveness of condenser is insufficient.

Symptom	Probable Cause	Diagnosis	Corrective Actions
Pressure is too high on both low and high pressure sides No air bubbles are seen through sight glass even when engine rpm lowers	Unable to develop sufficient performance due to excessive use of refrigeration system Cooling effectiveness of condenser is insufficient	Excessive refrigerant in cycle → excessive refrigerant was added during recharging Condenser cooling effectiveness is insufficient → condenser fins are clogged at cooling fan	Clean condenser Check the operation of the condenser cooling fan If 1 and 2 are normal state, check the amount of refrigerant and supply a proper amount of refrigerant

Air is present in the refrigeration system.

Symptom	Probable Cause	Diagnosis	Corrective Actions
Pressure is too high on both low and high pressure sides The low pressure piping is too hot to touch Bubbles can be seen through sight glass	Air in system	Air present in refrigeration system Insufficient vacuum purging	Check compressor oil to see if it is dirty or insufficient Evacuate the system and recharge it with new or purified refrigerant

Expansion valve malfunction

Symptom	Probable Cause	Diagnosis	Corrective Actions
Pressure is too high on both low and high pressure sides Frost or a large amount of condensation on piping on low pressure side	Expansion valve may be stuck	Excessive refrigerant in low pressure piping Expansion valve opened too wide	Check expansion valve

Insufficient compressor compression

Symptom	Probable Cause	Diagnosis	Corrective Actions
Pressure is too high on both low and high pressure sides Pressure is too low on high pressure side	Internal leak in compressor	Low compression Leak from a damaged valve, or parts may be broken	Replace compressor

Gauge readings (Reference)

REFRIGERANT ON-VEHICLE INSPECTION