Checking of Refrigeration System with Manifold Gauge (Cont'd) No. | Symptom seen in refrigeration system | Probable cause | Diagnosis | Remedy 7 | Vacuum indicated at low pressure side, very low pressure indicated at high pressure side Frost or dew seen in piping before and after receiver and drier or expansion valve | Refrigerant flow obstructed by moisture or dirt in refrigerant freezing or adhering to expansion valve orifice Refrigerant flow obstructed by gas leakage from expansion valve or heat sensing tube | Expansion valve orifice clogged Refrigerant does not flow | Allow to stand for some time and then restart operation to determine if trouble is caused by moisture or dirt. If caused by moisture refer to procedures Step 2 on page AC-18. If caused by dirt, remove expansion valve and clean off dirt by blowing with air. If unable to remove dirt, replace valve. Vacuum purge and charge new refrigerant to proper amount. For gas leakage from heat sensing tube, replace expansion valve. 8 | Pressure too high at low pressure side Pressure too low at high pressure side | Internal leak in compressor Valve leaking or broken sliding parts (Piston, cylinder, gasket, etc.) broken | Compression defective | Repair or replace compressor Discharging of Refrigeration System Evacuating and Charging of Refrigeration System (See Air Conditioning Fundamentals and Repairs Pub. No. 36950E)