Ok I'm going to tell you what I did on my RV... First. new the Q!@$!#@$E Furnace control was flakey.. The Front Carrier A/C (I won't bother to tell you to avoid Carrier as they don't make 'em any more for RV's) controlled the Furnace and the Thermostat was part of the A/C Ceiling uint.. Had to use a fan to tame it (Blow air from elsewhere in the RV)
So I found where the wires ran down the wall (Behind the master control panel logically) and tapped them.... Did not get around to the rest till the Carrier turned into a Coleman without furnace control
Then I got a simple mercury free mechanical Thermostat from Ace hardware (NO special recommendaton other than i think it was 20 bucks or less) This type uses a bi-metal spring and magnetic contacts (the magnets make it "Snap" open or closed) and wall mounted it.. Unlike the old no longer made Mercury bulb T-Stats this one need not be level. The one I had was heat only.
Add it with a SPDT toggle switch so you can control the furnace either with the Heat Pump system. or independent and you are golden.
