My ac unit on my rv keeps tripping the breaker when the compressor kicks in?

Probably a bad compressor, but it could be a bad breaker. Check the amp rating on the breaker and then use an ampprobe on the wire when the compressor starts. If you do not have access to an ampprobe and the experience to use it, take the unit to an RV service center. A new breaker might be $20, compressor at least 10 times that.