Refrigerant

ON−VEHICLE INSPECTION 1. INSPECT REFRIGERANT VOLUME

a. Observe the sight glass on the cooler refrigerant liquid pipe A.

Test conditions:

Running engine at 1,500 rpm
Blower speed control switch at ”HI”
A/C switch ON
Temperature control dial at ”MAX. COOL”
Fully open the doors

Item	Symptom	Amount of refrigerant	Corrective Actions
1	Bubbles present	Insufficient*	1 Check for gas leakage and repair if necessary 2 Add refrigerant until bubbles disappear
2	No bubbles present	None, insufficient or too much	Refer 3 and 4
3	No temperature difference between compressor inlet and outlet	Empty or nearly empty	1 Check for gas leakage with gas leak detector and repair if necessary 2 Add refrigerant until bubbles disappear
4	Considerable temperature difference between compressor inlet and outlet.	Correct or too much	Refer to 5 and 6
5	Immediately after air conditioning is turned off, refrigerant clear	Too much	1 Discharge refrigerant 2 Remove air and supply proper amount or purified refrigerant
6	Immediately after air conditioning is turned off, refrigerant foams and then becomes clear	Correct	−

*: Bubbles in the sight glass with ambient temperatures higher than usual can be considered normal if cooling is sufficient.

2. INSPECT REFRIGERANT PRESSURE WITH MANIFOLD GAUGE SET

a. This is a method in witch the trouble is located by using a manifold gauge set. Read the manifold gauge pressure when the these conditions are established.

Test conditions:

Temperature at the air inlet with the switch set at RECIRC is 30 − 35 °C
Engine running at 1,500 rpm
Blower speed control switch at ”HI” position
Temperature control dial at ”COOL” position
A/C switch ON
Fully open doors

1. Normally functioning refrigeration system.Gauge reading: Low pressure side:
0.15 − 0.25 MPa (1.5 − 2.5 kgf/cm2) High pressure side:
1.37 − 1.57 MPa (14 − 16 kgf/cm2)

2. Moisture present in refrigeration system.

Symptom	Probable cause	Diagnosis	Remedy
During operation, pressure on low pressure side sometimes become a vacuum and sometime normal	Moisture in refrigerating system freezes at expansion valve orifice causing a temporary stop of cycle, however, when it melts, normal state is restored.	Drier in oversaturected state Moisture in refrigerating system freezes at expansion valve orifice and blocks circulation of refrigerant	1 Replace condenser 2 Remove moisture in cycle by repeatedly evacuating air 3 Supply proper amount of new refrigerant

3. Insufficient coolin

Symptom	Probable cause	Diagnosis	Corrective Actions
Pressure low on both low and high pressure sides Bubbles seen thought sight glass continuously Insufficient cooling performance	Gas leakage in refrigeration system	Insufficient refrigerant Refrigerant leaking	1 Check for gas leakage and repair if necessary 2 Supply proper amount of new refrigerant 3 If indicated pressure value is close to a 0 when connected to gauge, create the vacuum after inspecting and repairing location of leak

4. Poor circulation of refrigerant

Symptom	Probable cause	Diagnosis	Corrective Action
Pressure low on both low and high pressure sides Frost on pipe from condenser to unit	Refrigerant flow obstructed by dirt in receiver	Receiver clogged	Replace condenser

5. Refrigerant does not circulate

Symptom	Probable cause	Diagnosis	Corrective Actions
Vacuum indicated on low pressure side, very low pressure indicated on high pressure side Frost or dew seen on piping before and after receiver/ drier or expansion valve	Refrigerant flow obstructed by moisture or dirt in refrigerating system Refrigerant flow obstructed by gas leaked from expansion valve	Refrigerant does not circulate	1 Check expansion valve 2 Clean out dirt in expansion valve by air blowing 3 Replace condenser 4 Evaporate air and supply proper amount of new refrigerant. 5 For gas leakage from expansion valve, replace expansion valve

6. Refrigerant overcharged or insufficient cooling of conden

Symptom	Probable cause	Diagnosis	Remedy
Pressure too high on both low and high pressure sides No sir bubbles seen through the sight glass even when the engine rpm is lowered	Unable to develop sufficient performance due to excessive use of refrigerating system Insufficient cooling of condenser	Excessive refrigerant in cycle"too much refrigerant supplied Condenser cooling insufficient"condenser fins clogged at cooling fan	1 Clean condenser 2 Check cooling fan with cooling fan motor operation 3 If 1. and 2. are in normal state, check amount of refrigerant and supply proper amount of refrigerant

7. Air present in refrigeration system

Symptom	Probable cause	Diagnosis	Corrective Actions
Pressure too high on both low and high pressure sides The low pressure piping too hot to the touch Bubbles seen through sight glass	Air entered in refrigerating system	Air present in refrigerating system Insufficient vacuum purging	1 Check compressor oil to see if it is see if it is dirty or insufficient 2 Evacuate air and supply new refrigerant

8. Expansion valve improperly

Symptom	Probable cause	Diagnosis	Corrective Actions
Pressure too high on both low and high pressure sides Frost or large amount of dew on piping on low pressure side	Trouble in expansion valve	Excessive refrigerant in low pressure piping Expansion valve opened too wide	Check expansion valve

9. Defective compression compressor

Symptom	Probable cause	Diagnosis	Corrective Actions
Pressure too high on low high pressure sides Pressure too low to on high pressure side	Internal leak in compressor	Compression failure Leakage from valve damaged or broken sliding parts	Repair or replace compressor

Gauge readings (Reference)

Refrigerant

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