Use a test probe (test light with a sharp point on it) and carefully penetrate the insulation on wire going to your compressor. Make sure the fan is on and the a/c is switched on first! If the test light goes on then the compressor's getting power and it's probably the magnetic clutch at fault. Also check that the compressor body is properly earthed. My Peugeot was getting power to the compressor but even though it was bolted to the block the earth was bad. I put on an extra earth wire and the clutch engaged right away.