Take it to someone who can do a proper vacuum and pressure test as well as add fluorescent dye to the system so that the leak may be localised using a blacklight.my air con worked when i brought my car. then it stopped.
regassed and to my surprise the next day it still worked. it lasts a day or 2 then stops working again
i hate small leaks is this probably a seal somewhere?
the fan and compressor work fine