We spend the winter in St.Augustine Florida therefore seldom use our Oasis fired furnace. But I regularly check things just to be sure they work if I need them. The other day, when it was cooler, I tried to set the Dometic thermostat for zone 1 and 3 to the "Furn" setting to make sure that function was operating as it should. Zone 1 was set but zone 3 didn't even show the "Furn" option on the thermostat display. We used the furnace several times this year while in Alaska and out west so I know it was available and functioning earlier this year. We did have to replace the third A/C unit in the fall and it was supposedly replaced by an identical unit as the original. My questions... does anyone know if this might indicate a thermostat issue, or should I be looking for a loose wire from the A/C unit?