carl dye test the system. valve cores and compressor leaks very common. some times if leak is bad enough u can hear it. you can also put ur thumb over the valves to feel for back pressure. soapy water in spray bottle is your friend too.

m7x if you repair system with ebay kit be sure to properly flush evaporator and lines. if theres crap in the system u may have to replace the condenser. you cant properly flush a parallel flow condenser.