HVAC 29 REFRIGERATION CYCLE TROUBLESHOOTING Sr. No. POSSIBLE CAUSE REMEDY 3 Entry of moisture in the refrigerant cycle Condition Air conditioner alternately cools and does not cool. Symptoms in refrigerant cycle During operation, the pressure on the low pressure side alternates between vacuum and normal. Cause The moisture mixed in the refrigerant in the refrigerating cycle freezes in the expansion valve orifice, blocking the cycle. After a time, the ice melts and normal conditions return Diagnosis The drier is in an oversaturated condition. The moisture in the refrigerating cycle freezes the expansion valve orifice, impeding refrigerant circulation. Countermeasures Remove the moisture by repeated evacuation. Recharge new refrigerant to the specified amount. 4 Refrigerant fails to circulate Condition Air conditioner does not cool. Symptoms in refrigerant cycle Pressure on the low pressure side is vacuum Pressure on the low pressure side is vacuum low. Frost or dew is formed on the piping at the front and rear side of the receiver or the expansion valve. Cause Moisture or dirt in the refrigerating cycle freezes or sticks to the expansion valve orifice, obstructing refrigerant flow. Gas leaking from the heat sensitizing tube of the expansion valve obstructs refrigerant flow. Diagnosis Blocked expansion valve orifice. Countermeasures Allow to stand for some time and then resume operation to decide whether the blockage is caused by moisture or by dirt. If caused by moisture; remove the moisture by repeated, Recharge new refrigerant to the specified amount. If cased by dirt; remove the expansion valve and blow out the dirt with compressed air. If unable to remove the dirt, replace the expansion valve. Evacuate and charge new refrigerant to the specified amount. If caused by gas leaking from heat sensitizing tube, replace the expansion valve.
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