>>28456363
First thing is a thorough underhood inspection looking for oily build-up on A/C components, particularly hose crimps and the most exposed areas of the condenser. There will be some fresh oil on the charging ports since somebody was just there but if there's black oily dirt surrounding that then that may indicate a leak there. Any parts with oily build up indicate a leak and need to be replaced.

If everything looks dry then it suggests an evaporator leak, or at least a leak inside the evaporator case so you would need to get the system charged with a dyed refrigerant if it wasn't already, and run it for a couple hours and then use one of those kits with a black light and yellow goggles to look for dye coming out of the A/C condensate drain from under the car. Also double check every hose and connection under the hood with this too. BTW there are halogen leak detectors but that could detect a leak in seconds but they're too expensive for a backyarder so the dye is pretty much your only choice.