The compressor has a LOUD clicking noise. I can turn on the AC and the noise stops,, Turn it off and the noise returns. I've never messed with the internal parts on a compressor. What could it be? Thanks, Joey

It sounds like a problem in the compressor clutch, not the internals of the compressor. When you turn the A/C on, the clutch engages and spins the inside parts of the compressor, when it's off, just the pulley and outer clutch parts are moving. Something may have come apart and is hanging up between the clutch plates making the noise. If you'll buy the factory Chassis Overhaul Manual, it will have instructions on repairing the compressor.
BillL