You have a leak. Could be as simple as one of the schrader valves leaking( the high or low side where the caps are) which is easily replaceable with a new core, or it could be a leak from corrosion on the condenser behind the bumper for which there is a specific TSB for. In order to really tell from where it is leaking from, some UV dye has to be injected and system refilled and cycled then checked with a blacklight to see where the glow of the dye leaking out is. Then go from there.
