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 ↓ 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 ↓ 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 ↓ 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 ↓ 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 ↓ 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.