Hi !
Welcome to IRV2! We're sure glad you joined the gang!
Have you done the factory-recommended reset on the thermostat?
If you have the flat, 4-conductor telephone line to the thermostat then the plugs on each end could be corroded. You can unplug and replug them several times to clean the contacts. You do this with the thermostat turned off of course. You will probably have the same cable running between the two A/C units.
Good luck, happy trails, and God bless!
__________________
Joe & Annette
Sometimes I sits and thinks, sometimes I just sits.....
2002 Monaco Windsor 40PBT, 2013 Honda CRV AWD