Nobody asked yet, but here's why I didn't readily make the connection between one of the two FFs in the ceiling and the wall thermostat....
The latter is in the eaxct same place and looks identical to the thermostat in our old Pace Arrow. In the Pace, that thermostat controlled the propane-fuelled heating. The roof a/c units, which also had electric heat strips, were controlled by another box in a different location. I just assumed that this coach was the same and that the dealer had upgraded the a/c control to a combined heat and a/c controller, disconnecting the wall thermostat in the process.
I played with that thermostat until it almost fell off the wall, trying get the heat on &/or trying to control the temperature before I figured out it didn't do anything and coming to the conclusion that the dealer had installed the upgrade.