Agree with Fred, Capacitor... The Compressor and the Fan, each need their own RUN capacitor. Sometimes they're individual capacitors with their common terminals connected with a jumper. Sometimes they're a combined capacitor. Your Compressor uses the higher value of the two. Say 35mfd and Fan 5mfd. If it's a combined capacitor, the Compressor side might be marked HERM (for the hermetically sealed compressor and coils) and the Fan marked FAN.
I just wonder if your AC unit also has a Start Assist Device. That's a third capacitor, usually plastic, 88-100mfd, and a device to take it out of circuit once the compressor has started. Some feature of the Start Kit may have failed.
Are you running your AC off a campground-type 30-amp circuit, heavy cord, or say a generator? Campground with proper RV cabling should give you a good start.
Please try what Fred suggests, and post a pic of the capacitor area of your AC unit. Then we can see if it's got a start kit also. You might see a wiring diagram pasted on the unit, photo that too, and get the Make/Model info. All that'll help us help you if the quick capacitor swap doesn't get it.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB