I am not sure what a 2004 24b Dutchmen is. I could not easily find one on-line.
Actually we need make and model of your furnace.
Most low end travel trailers have a simple furnace system. Is yours a low end travel trailer?
Thermostat is a simple switch. Connection is either "on" or "off".
Thermostat can be stuck "on".
Disconnect one wire.
See if furnace stops. If so, replace thermostat.
There are other possibilities.
Bad control board
Failed temperature switch inside furnace
Other RV's can have complicated thermostats integrated with A/C. Is yours integrated with A/C?
Dutchman Kodiak Cub KD176RD 2018
Nissan Pathfinder 2015