Disconnect the a/c compressor harness from the a/c compressor.
Put a fuse in the fuse panel. If the fuse blows it means you have a short in the harness. It does not mean the a/c compressor is good, you will come back to that later.
Use an audible circuit breaker, a multimeter with an audible continuity circuit, or the ohm function of the multimeter to test the power out side of the a/c circuit. You will need to probe along the ciruit until you find the short. A short is power going directly to ground, and that is what causes the fuse to blow. You will have to look for bare wires, melted insulation, etc.