Are you talking about a gas heater, or is it a heat function built into the roof air conditioner? If it is a heat setting in the air conditioner, some do not cycle for temperature control. These are either on or off with the temp knob having no effect on the heat strip. We had one like this on a popup we had. The only temp control was to partially open a window when it got too hot.
Robert & Nancy with "Murphy the EOG"
Murphy has passed on, but Micah and Bogie have assumed the watch! 02 Holiday Rambler 5ver, 2015 Indian Chief Vintage. 98 Coachmen truck camper.