I replaced this Dometic 13 k btu AC with a Furrion Chill-cube unit. Since the old T stat worked both furnace and AC via control in the AC unit my T stat shows an error E1 and heat will not work. I purchased a new two wire T stat but the wiring from old config is a three wire (+)(-)12vdc and a return to old AC. Then there was a two wire to furnace. The wire going to furnace is reading 12 vdc now. Does anyone know how to connect the propane furnace to work off of new T stat?