HELP! Compressor now trips breaker on start up??

Yes, the compressor worked fine until I wired in the switch. I used a 20 amp light switch and 20 amp receptacle. 12/3 wire. Breaker is brand new. Also hooked up a 30 amp breaker, and the same thing happened. I pulled the capacitors out, but they look good. I will get them tested on Monday and replace if needed.