Not sure how close your tstat is to the one in my '05--but the furnace only runs on zone 1, unless you have heat pumps--then I don't have any ideas.
Use the mode button to select fan only, AC, or furnace. If you have mode on auto, the unit is going to come on/off as it sees fit.
Of course, if you don't need either heat or air, then just turn everything off with the main switch.
Let us know what you come up with.
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired