Hey, I assumed that you charged it up with freon? They have cheap kits at the auto parts stores. If it doesn't have freon in it, then the compressor won't kick on. What I do is hook up the freon, turn on the car with A/C on high, then run a jumper wire from the battery to the compressor (there will be a single wire coming off the compressor to a connector on the fan shroud). Try that, see what happens.