(2) Diagnosis by pressure gauge
Standard pressure value
With the storage temperature at about 0°C
– 43 –
Refrigerant
pressure
High pressure
Low pressure
[Condenser entrance air temperature] + Saturation
pressure of about 14 ~ 16°C
[Cool wind entrance temperature] - Saturation pressure
of about 20°C
No. Pressure Main causes
1
2
3
4
5
6
Both high and low pressure are too high
High pressure is rather low and low pressure is
too high.
High pressure is rather high and low pressure is
too high.
High pressure is almost normal but low pressure
is too low. (Evaporator becomes frosted.)
High pressure is too high but low pressure is
almost normal.
Both high and low pressure is too low.
1. Excessive refrigerant (Accompanied by backing of liquid)
Take out refrigerant up to a fixed amount.
2. Storage temperature is very high.
1. Suction of compressor is defective due to cracking of valve.
(Repair)
1. Excessive opening of expansion valve (Adjust).
2. Contact of expansion valve thermo cylinder to suction pipe is
defective. (Correction)
1. Refrigerant is al little short. (Charge refrigerant)
2. Clogging of receiver dryer or dryer, and expansion valve.
(Replace and adjust)
3. Evaporator fan is defective. (Repair)
1. Condenser is dirty. (Clean)
2. Amount of wind of condenser is short
3. Outside temperature is high
4. Incompressible gas is mixed in the unit. (Vacuumizing, gas
charge)
5. Fan for condenser is defective. (Repair)
1. Refrigerant is extremely short. (Charge refrigerant)
Expansion valve is making a hissing sound.
2. Outside temperature is low. Excessive amount of wind
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