Okay, due to my big mouth and willingness to help I am now in over my head. I just hated to see a pricey unit thrown away over a start relay. Problem is the terminal welded to the compressor pin. I thought it was coming off until I pulled the pin out of the compressor! Chalk that up to stupidity and no good deed goes unpunished.
So I need a little help understanding what symptoms I'd see if a critically charged system was under or over charged. There is no data on charge weight.
I'm tending to think if one charged a small system during cooler temperatures one might find as the ambient air goes up you are no longer geting a column of liquid to the cap tube. At the other extreme I guess one could stack the condenser totally full of liquid once ambient air temps dropped.
I really have no idea what sub cooling and superheat numbers I'd be looking for on a small lab refrigerator running 134a. I'm guessing like 10 degrees superheat and upwards of 20 degrees subcooling?
BTW, if the system has a receiver and expansion valve need I give any more thought than getting a clear sight glass and maybe adding enough extra to get 10/20??? degrees of sub cooling?