
AC-18
AIR CONDITIONING SYSTEM — Troubleshooting
Checking of Refrigeration System with Manifold Gauge (Cont'd)
No. | Symptom seen in refrigeration system | Probable cause | Diagnosis | Remedy
1 | During operation, pressure at low pressure side sometimes becomes a vacuum and sometimes normal | Moisture entered in refrigeration system freezes at expansion valve orifice and temporarily stops cycle, but normal state is restored after a time when the ice melts | Drier in oversaturated state
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Moisture in refrigeration system freezes at expansion valve orifice and blocks circulation of refrigerant | (1) Replace receiver and drier
(2) Remove moisture in cycle through repeated vacuum purging
(3) Charge refrigerant to proper amount
2 | Pressure low at both low and high pressure sides
Bubbles seen in sight glass
Insufficient cooling performance | Gas leakage at some place in refrigeration system | Insufficient refrigerant in system
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Refrigerant leaking | (1) Check with leak detector and repair
(2) Charge refrigerant to proper amount
3 | Pressure low at both low and high pressure sides
Frost on tubes from receiver to unit | Refrigerant flow obstructed by dirt in receiver | Receiver clogged | Replace receiver
4 | Pressure too high at both low and high pressure sides | Unable to develop sufficient performance due to excessive refrigerant in system
Condenser cooling insufficient | Excess refrigerant in cycle → refrigerant overcharged
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Condenser cooling insufficient → condenser fins clogged or fan motor faulty | (1) Clean condenser
(2) Check fan motor operation
(3) If (1) and (2) are normal, check refrigerant amount
HINT: Vent out refrigerant through gauge manifold low pressure side by gradually opening valve.
5 | Pressure too high at both low and high pressure sides
Frost or large amount of dew on piping at low pressure side | Trouble in expansion valve or heat sensing tube not installed correctly
Refrigerant flow cut off | Excessive refrigerant in low pressure piping
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Expansion valve opened too wide | (1) Check heat sensing tube installation condition
(2) If (1) is normal, test expansion valve in unit
(3) Replace if defective
6 | Pressure too high at both low and high pressure sides | Air entered refrigeration system | Air present in refrigeration system
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Insufficient vacuum purging | (1) Replace receiver and drier
(2) Check compressor oil to see if dirty or insufficient
(3) Vacuum purge and charge new refrigerant
*Note at No. 6
These gauge indications are shown when the refrigeration system has been opened and the refrigerant charged without vacuum purging.