Have RV Questions? Ask an RV Mechanic Online.
Welcome, I'm Chris (aka Moose) I prefer to work when others don't, I am here around lunch and after dinner till after midnight.
Sometimes a reset is whats needed. Disconnect the plug from the breaker outside and disconnect the negative battery cable from the RV battery. Turn off all breakers. 20 minutes later reconnect the battery. Plug in outside. Turn all the breakers on one by one. Try this and let me know the results.
This is my 1st answer, but does not have to be my only answer. You the website and myself expect you to have a ~~~5 STAR EXCELLENT~~~ experience with my help. Please let me know if you are pleased by selecting a star rating above or by replying and saying your pleased. Not rating or rating 1-2 stars does not benefit you nor me in any way. Follow up and reply as often and when needed, there is no extra charge to do so.
It still is a communication error between the thermostat and AC unit(s) I do not like this electronic thermostat, I like the manual ones, they fail less. I do not believe I am going to be able to help you diagnose this at an RV site. I will opt out and see if another feels like they can get you running. Your post will be placed back on the board open for all to see. I doubt anyone will respond at this time of the night though. Best of luck.
Is this a Dometic Single Zone thermostat? And do you have a small digital multimeter for some testing? That would be the quickest way to track this down. About $20 or so at most hardware stores and easy to use. Model of your A/C would be helpful as well.