I was working on a masterbilt walk in cooler r-22 dual evaporator ive been there 2 times manager says it wasn't cooling when he gets in but everytime ive been there it was down to temp. I thought it might be the defrost set for too long it was originally set for 12am and 12pm 45mins in defrost so i set it for 25mins defrost then i got called back on sunday and temp was 57 degrees and not droppping my condenser was running i had a 10 suction and a 150 head i checked my pipe temp at oulet of both evaps it was 56 degrees so i thought maybe my liquidline solonoid might be having issues so i took the temp on the inlet and out let i was getting 92 degrees, and checked if my solonoid was gettig voltage and energizing it was so i added some refrigerant to see if pressures went up i added 5oz of refrig and my compressor made a noise like it had a high load and then my pressure went to normal had 45 suction and 180head and started cooling the box down i dont think it was low on charge does anyone have any ideas what could be going on? i have a feeling ill be getting that call back im an a/c guy and new to refrig and advice is greatly apperciated