HEXA

HVAC 40 REFRIGERATION CYCLE TROUBLESHOOTING Sr. No. Possible Cause Remedy 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 condi- tion.  The moisture in the refrigerating cycle freezes the expansion valve orifice, im- peding refrigerant circulation.  Recharge new refrigerant to the specified amount. 4 Refrigerant fails to cir- culate Condition  Air conditioner does not cool. Symp- toms 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 Condition. Countermeasures  Allow to stand for some time and then resume operation to decide whether the block- age is caused by moisture or by dirt. If caused by mois- ture; remove the moisture by repeated, Recharge new re- frigerant 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 speci- fied amount. If caused by gas leaking from heat sensi- tizing tube, replace the expansion valve.