Air conditioning problem

If there are no other problems and the leak has been repaired, you need to pump the system into a vacuum for at least half an hour to boil out any moisture. Water in the system will cause intermittent cooling, and will form acid that will corrode metal parts.

With no pressure in the system, the low-pressure cut-out switch will prevent the compressor from running. That will prevent the low side from going into a vacuum and potentially drawing in outside air and the humidity in it. You need to bypass that switch or bypass the compressor relay to make the compressor run. If you still have a hard time getting the full charge to go in, set the can in a pot of hot water.