under dash a/c

The under dash unit should contain a fan and switch. Make sure that fan runs and doesn't make excessive noise. If that much is good you will ten need compressor which brakets, a drive belt, condenser, reciver dryer, hoses, and expansion vlave. it sounds like a lot, it is a lot. A complete new system might be better than completing what you have. LIke computers, it cost more to build one than to buy off the shelf.