Need alittle help on a residential compressor

[HV Mech]

I had a friend call me and said his breaker on his outdoor compressor keeps tripping. He resets it, it runs for a little while then trips again. I told him to change his breaker. He did and when he turned the system on it now trips immediately. I went over and tested his compressor and got no resistance on anything. c-s, c-r and s-r. I replaced the compressor and when i turned power back on it tripped immediately again. I replaced the capacitor and its still tripping. When i pull the start wire from the capacitor i can get the fan to run, but when i connect it, the breaker trips again. I also checked to make sure the compressor isn't grounded. This is a 5 yr old system and no work has been done recently. I checked the wires to make sure nothing is bare and touching metal. HELP! I'm at a lost

[FEISTY]

Let's keep it simple to start. First, isolate each electrical device. Ohm out wire by wire but remember to disconnect one end and go to a good clean ground. If you take the compressor out of the wiring circuit , cycle the fan. If it runs, take the fan out of circuit and try compressor. It sounds like you have a direct ground since the breaker trips instantly. By the way...you said you changed the capacitor AFTER you trid the new compressor. My rule is ...new compressor...all new start components. That includes contactor. If the old comp failed and was in need of replacement...so do the electrical parts. Lastly if you are using a fused unit disconnect at the unit, change the fuses also. Just consider a changeout a complete changeout. Good luck.