On-Vehicle Inspection

INSPECT REFRIGERANT VOLUME

Check the sight glass on the air conditioning tube & accessory assembly.

Prepare the vehicle according to the chart below.

SIGHT GLASS ON AIR CONDITIONING TUBE & ACCESSORY ASSEMBLY

Item	Condition
Vehicle door	Fully open
Temperature setting	MAX COLD
Blower speed	HI
A/C	ON

Fig 1: Identifying Sight Glass On Air Conditioning Tube And Accessory Assembly

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Compare the sight glass to the following chart.

SIGHT GLASS REFERENCE CHART

Item

Symptom

Amount of refrigerant

Corrective Actions

Bubbles exist

Insufficient⁽¹⁾

Check for gas leakage and repair if necessary
Recharge with proper amount of refrigerant

No bubbles exist

Empty, insufficient, or excessive

Refer to 3 and 4

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 the proper amount of refrigerant

Considerable temperature difference between compressor inlet and outlet

Proper or excessive

Refer to 5 and 6

Immediately after air conditioning is turned off, refrigerant remains clear

Excessive

Recover refrigerant
Evacuate the AC system and recharge with the proper amount of refrigerant

Immediately after air conditioning is turned off, refrigerant foams and then becomes clear

Proper

⁽¹⁾	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

HINT:

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 established.

Test conditions:

Temperature at the air inlet with the switch set at RECIRC is 30 to 35°C (86 to 95°F).
Engine is running at 1,500 rpm.
Blower speed control switch is at "HI".
Temperature control dial is at "COOL".
A/C switch is ON.
Doors are fully open.
Ignition switch is in a position that enables the AC compressor to run.

Normally functioning refrigeration system

Gauge reading

NORMALLY FUNCTIONING REFRIGERATION SYSTEM - 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)

Fig 2: Checking A/C Refrigeration Pressure

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Moisture is present in refrigeration system.

Fig 3: Checking A/C Refrigerant Pressure When Moisture Present In Refrigeration System

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NORMALLY FUNCTIONING REFRIGERATION SYSTEM - MOISTURE IS PRESENT IN REFRIGERATION SYSTEM

Symptom	Probable Cause	Diagnosis	Corrective Actions
During operation, pressure on low pressure side cycles between normal and vacuum	Moisture in 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

Fig 4: Checking A/C Refrigerant Pressure For Insufficient Cooling

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NORMALLY FUNCTIONING REFRIGERATION SYSTEM - 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 leakage 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

Fig 5: Checking A/C Refrigerant Pressure For Poor Circulation Of Refrigerant

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NORMALLY FUNCTIONING REFRIGERATION SYSTEM - 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.

Fig 6: Checking A/C Refrigerant Pressure For Refrigerant Does Not Circulate

NORMALLY FUNCTIONING REFRIGERATION SYSTEM - 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 the 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.

Fig 7: Checking A/C Refrigerant Pressure For Refrigerant Overcharged Or Cooling Effectiveness Is Insufficient

NORMALLY FUNCTIONING REFRIGERATION SYSTEM - REFRIGERANT IS OVERCHARGED OR COOLING EFFECTIVENESS 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 proper amount of refrigerant

Air is present in refrigeration system.

Fig 8: Checking A/C Refrigerant Pressure For Air Present In Refrigeration System

NORMALLY FUNCTIONING REFRIGERATION SYSTEM - AIR PRESENT IN 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

Fig 9: Inspecting Refrigerant Pressure With Manifold Gauge Set - Expansion Valve Malfunction

NORMALLY FUNCTIONING REFRIGERATION SYSTEM - 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 sticking	Excessive refrigerant in low pressure piping Expansion valve opened too wide	Check expansion valve

Insufficient compressor compression

Fig 10: Checking A/C Refrigerant Pressure For Insufficient Compressor Compression

NORMALLY FUNCTIONING REFRIGERATION SYSTEM - INSUFFICIENT COMPRESSOR COMPRESSION

Symptom	Probable Cause	Diagnosis	Corrective Actions
Pressure is too high both on 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)

Fig 11: Gauge Readings (Reference) Graph