To check this or verify for your self unhook power to the unit Then take the wires off the compressor. Then use an ohm meter and go from each terminal to the body of the compressor. If you pick up a reading or the meter zero's you have a grounded out compressor. Next step is why did it ground out? Sometimes age but most often something caused a slow death like poor airflow , low charge incorrect wire size. There are may reasons. A good tech can tell you why it went out not just that it is bad.
Let me know if you need more. if the compressor checks good this way check for resistance across each of the three terminals. the two lowest readings should equal the highest reading. I am assuming this is a residential system.
Thank you Richard