AC electrical problems

Is this what you have in black?
Thermostat
Here is manual stating where fuse is located.
RV comfort ZC manual

it just says rv.comfort. zc

Can you post make and model of the thermostat?

THe thermostat is a very simple black box...no fuse inside

Have you tried resetting the thermostat?
Open thermostat to expose fuse on circuit board, remove fuse and wait 15-20 seconds, re-install thermostat and have the system reboot itself. This could take 15-20 minutes.

Only the back AC kicks off, can come back on or it then stays off. I go outside, unpluug, count to 30 slowly, plug back in and that seems to resolve things, at least for a while. This tends to happen more when it is very hot and sunny, less so or not at all on rainy, cloudy or cooler days. Any thoughts? Our termostat dors not look like htat at all, very simple one.

Two posibilities, If you have a load shedding energery manager like the one photoed above.. Suspect #1

My story (I do not have one of those) Sometimes front A/C worked, sometimes rear sometimes both..... Finally got to trouble shooting.

First stop: The power distribution (Breaker) box (Also the last stop)

Several screws which hold the wires in the clamps were loose, like over two turns loose on one of them... Yup, that was the problem..

I keep saying many RVers have a few screws loose.. In my rig those take a #2 Square Bit.

Well your not alone. We are having same type of issue.My name is Bud and we recently went from a 2007 Thor Mandalay M40g with yes some problems traded it for a 2008 Mandalay M40hall was well for the first trip had the same issue but we had a bad transfer switch that was under a recall and Thor took care of it no charge thanks T.M.C. All was good till the second trip when it happened again. We keep it plugged in at home to a 50amp service has a surge protector, when we go away I test power supply with a meter and it's good. So this time drove 2 hrs. generator on both a/c's working and very cold cycling on and off all is good July 3rd. it's 95 and we live in So Fl. plugged in like usual shut off gen. landing gear I call it open slides and within a 30 min. both a/c's go off at same time thermo goes blank and have apparently inverter power only as a few outlets etc. Tried generator, tested transfer switch had power through the power cord as surge protector was lit and power through it (correct power and flow no faults) I tripped reset all breakers all good. Getting ready to cancel trip as it's so hot then a/c's came back on after 3 hrs. All worked for the rest of the weekend no problem. The next weekend I set a/c's and was outside detailing coach all was fine maybe 90 out a few hours later went in to cool down no problem then as before both a/c's shut down this time I waited went in an out several times then said screw it shut every thing off, unplugged and went in house. Next day went on roof took covers off a/c's and found 2 mud dobber nests in each a/c coil about 2"x5" cleaned them out real well blew out coils with air from coach put covers back ran a/c's to check and shut off. Next weekend brought into shop they road tested, had gen.on/off shore power slides open closed run and even set to 70. They checked power cord and surge protector good check circuit panel good as them to look at P.M.S. power management as of 8/15/14 they have not been able to duplicate the problem as of yet today 8/16/14 I pick it up i'll road test it set up in yard as I do and run everything as I would be on a trip. Oh boy I get to camp out in my back yard!!! Will let you know if problem exists.

Do you have an on-board generator? Will both ac units operate when you run the generator?

Does your thermostat look like this?

That sounds like your EMS is doing some load shedding. That is if you have an Energy Management System? Slim possibility that the thermostat could also do that. There souldn't be amything in the line voltage that would automatically restart a load like that.What else is on when this happens?