Have a small countertop cooler that is used for salads. etc. Kept at 36 to 40 F. Small hermetic featuring 134a. Few weeks ago, ceased to cool One of our guys added schraders on both sides and charged, but nobody can find the leak. My question: factory plate states 6 oz., but starting from situation where system is not evacuated, howdoes one adjust to the optimum charge. What should the superheat be on this sytem. By the way, it's cap tube.Obviously, I'ma boobie, so go easy on me, ha ha. Thanx in advance>