My fan runs all the time; the compressor cycles. It's a very basic AC unit with all the controls on the unit in the ceiling; no ducts.
When I first got it I didn't like it; I didn't see the need for the fan to run all the time. So, I rewired it so the fan and compressor cycled on and off together. This didn't workout well. The camper would feel really hot and stuffy without the fan. Then it would all come on and cool it way down. Then, it would warm up and feel hot and stuffy again. Also, the noise coming on and off would kind of wake me up sometimes at night.
I put the wiring back the way it was so the fan just runs all the time and the camper stays nice and cool.