Dometic AC unit

Mine has done similar when fan is on auto. Set to either low or high.

Where is the thermocouple? Pull the panel off, and make sure the thermocouple is in the air flow. I bent mine about 30 deg forward into the airflow and it works perfectly now.

brnthumbinfl wrote:
...the unit will cycle on for as little as 10 seconds then cycle off for 10 seconds. Back and forth...

Perhaps it is the differential temperature setting - see LINK

brnthumbinfl wrote:
We purchased our 2019 Mesa Ridge 21RBS TT from Lazy Days in Tampa, January 2019. We've had it in twice for warranty repairs. Both times, we reported the AC unit would hover when it reached the set temperature. Particular at night, the unit will cycle on for as little as 10 seconds then cycle off for 10 seconds. Back and forth as many as a dozen times. The unit is not terrible quiet, so this gets irritating when you're trying to sleep. Plus it can't be good for the unit.

Lazy Days checked it twice without finding anything wrong. Of course it was winter when the unit isn't really working. They tried insulating the thermostat, then I forced them to replace the thermostat. Neither action corrected the problem. Currently I am beginning to think it may be the unit itself. It seems when it goes into hover mode, I'm not sure its really cooling as the air seems just room temp.

Any ideas?

Brnthumb

Are you sure it is doing it a "dozen times"
If you read your manual, you'll find out that it is normal and is adjusting itself to a lower speed once it reaches the set point.

Guy

I would try using a different ceiling assembly, which has the controls in it, and see if that correct issues.
An RV seller is ill-equipped to do any meaningful repairs and unlikely they have the ability to delve into refrigerant levels or pressures.
If you could check the coolant levels that would be great. I am not sure these roof ACs allow you to check as you would on a car or a house.

All AC units are basically the same, so a guy that can work on an AC will be able to work on any AC.

Is your compressor actually running, or just trying to start and giving up? You will hear the strain as the compressor tries to kick on, and then it smooths out a little when running. A 10 second cycle will not work on any unit. After the compressor kicks off the system needs time for the pressures to euqualize inside the pipes. The high pressure side will have too-high of pressure for the compressor to overcome and start. This is why you not supposed to turn temp up (making compressor turn off) then turn temp back down seconds later. Compressor will struggle to start, it might start, but that struggle is bad for the compressor.
On that note, there could also be an issue with your 2-stage starting capacitor. losse or coroded wires, bad capacitor...lots of youtube videos on this.

May well be normal. AC fan runs on high until it reaches set temp. Unit shuts off and comes back on with fan speed on low. Cycle can continue several times especially when temps are high