My RV ac compressor starts, i min. Later it stops.

SOURCE: PROBLEM WITH DOMETIC RV ROOFTOP AIR conditioner

Check at the compressor terminals between the Red and the terminal for the overload protector to see if you are getting power to the compressor on startup.

SOURCE: RV air conditioner. Compressor running, fan stops before cool

The fan motor is getting hot and going off on the internal overload in the motor.
This is caused by either a low voltage, a bad capacitor, or tight or dry bearings in the motor.
To check the bearings turn the power off to the unit, then spin the fan blade if it spins freely then the bearings are ok.
To check the capacitor you will need some kind of tester or you can buy a capacitor and replace it, that's what a lot of people do. They usually don't cost very much.
To check the voltage you will need a voltmeter and measure the volts at the unit.

SOURCE: RV Rooftop AC Unit

Sounds to me like your fan is hitting something
Remove the cover and turn the fan by hand ( with the power off ! ) See what it is hitting

SOURCE: My rooftop AC RV air conditioner will not start.

You can take a digital meter and put a lead on each
side of capacitor, the meter reading will go up and
then back down, Reverse the leads and it should do
the same thing.

If this is a dual capcitor that controls the fan and
compressor and only the fan comes on, more than
likely it is not the capacitor. However its easier to
replace the capcitor and prey to god that it works.

If it doesn`t then you know you have other issues for
sure, however the capacitor is a pretty cheap part.

SOURCE: air is not very cold on a rv roof top ac what

You should have the manual for this unit handy and as far as recharging tools go. You only need a can of R134a *(if the unit is R12 you need to buy upgrade adapters since R12 is no longer sold) Run the unit and put the R134a filler line on the low pressure side of the compressor *(from manual...dont guess as trying to charge the high pressure side is VERY dangerous). Get the charge just into the Green zone on your charger and that is it! Try not to fill too high in the green zone....I know it sounds funny...but AC's usually work better when they have the low end of their optimum fill. R134a doesnt work as well as R12 so be sure you buy the R134a with cooling enhancers. Your local Autozone can guide you to the right filler/product combination.

Good luck and be careful!