1999 Chrysler 300 A/C blows warm

Engine totally rebuilt, but b-4 that car sat for a year. A/c worked great for a few weeks then nothing. Feon full and no leaks. A/c compressor works and one line is cold. Tried testing blend door aculator, and change temp right away, wondering if it is the a/c expansion vavle (how to test this) or can it be anything else. Need help ASAP!