FATC 35 Sr. No. OCCURANCE POSSIBLE CAUSE REMEDY 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 5 Expansion valve malfunctioning (opening too much). Condition • Air conditioner does not cool effectively. Symptoms in refrigerant cycle • Pressure on both the low and high. Pressure sides is high. • Frost or heavy dew is formed on the piping on the low pressure side. Cause • The expansion valve is malfunctioning Diagnosis • Excessive liquid refrigerant in the low pressure side piping. • Expansion valve opened too far. Countermeasures • Check the diaphram of expansion valve. • If the diaphragm is proper, replace the expansion valve. 6 Faulty compression of compressor Condition • Air conditioner does not cool. Symptoms in refrigerant cycle • Pressure on the low pressure sides is too high and pressure on the high pressure side is too low. Cause • There is leaking in the compressor Diagnosis • Faulty compression of compressor. • Delivery valve or packing is leaking or broken or compressor is malfunctioning. Countermeasures • Check the compressor oil for contamination and quantity. • Replace the compressor.
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