You might have a bad ground somewhere. I don't know if the clutch uses a wire in the connecter as a ground or the body of the compreser as a ground, but it'* something to think about. Try checking the resistance between the compresser body and the negative terminal of the battery and (if one of the compresser wires is a ground) the resistance between it and the negative on the battery.
With a new compresser and you manually jumping the clutch wires with 12 volts, I would imagine that that could be the only possable cause. (other than a really bad clutch)