You still need to run the furnace to move warmed are through the enclosed underbelly.Winterizing mitigates the need for that furnace to keep the pipes from freezing. The furnace, the heating pads, a water tank that is hot all work together to keep things from freezing. If you don't have one of those items going it makes things sketchy.
2016 Rockwood 2703WS Sapphire
2016 F250 SD 6.2L