Air Conditioning - compressor diagnosis

60 amp circuit breaker trips instantly but no shorts to ground exist across either start, run, or common leads. (Local contractor performing tests and showing me 'cuz he thought it was a head scratcher)

He put amp meter and unit does draw 60+ instantly with no sounds indicating that it is jammed or attempting to start etc.

He feels must be internal short (eg. start coil shorted to run coil) and says I have to replace unit.

Any thoughts?

Thanks
Randy

Take your meter and set it to ohms. Take a reading between the windings and post them here. Do S+R, S+C, R+C . Then do the same from each post to the copper refrigerant line and post if the neddle or numbers go up on the meter. Or else get a 2nd opinion.

** Make sure the electric is OFF and remove the wires from the compressor.

He must not be much of a tech if he couldn't diagnose the problem.

What size is your unit? Post model and serial and Make.

He thinks he did diagnose it...by process of elimination. No shorts to ground found (I don't know if it was to pipe or to electical ground) but huge current draw (full 60 amps). He checked caps and other items. Lo Voltage relays seem fine.
He did not show me that he compared resistance but he said that all 3 (run, start, common) leads showed short to each other but said that they should. They are tied together internally and he pointed to schematic showing internal ends of start and run windings connected to protection (breaker?) on common. So it makes sense to me that they should all read dead short to each other even when all is well. I imagine that an impedance meter could detect shorts in middle of windings but I don't see how resistance would show anything. (I'm an audio/video guy so my electronics knowlege for this forum is just enough to get me in trouble.)

I guess I should get second opinion. I want to use this guy cause his shop is right down the street. He said something about split zones that I question though. I'll search here and post another question on that if need be.

Thanks
Randy

I would definitly get a 2nd opinion on it. Could just need a start kit installed but at the same time the compressor could be siezed up.

If you have an ohm meter capable of reading <10 ohms, you can ohm out the windings yourself. Check the terminals as follows: Common to Start (record reading), Common to Run (record reading), & Start to Run (record reading). C to S + C to R should equal S to R give or take an ohm or so.