RV Repair: Replacing thermostat, types and models, dometic

Question
We need to replace our thermostat.  Original was a Dometic DuoTherm Comfort Control multi mode which regulated two basement ACs and the furnace.  We replaced ACs with manual operated roof air a few years back so thermostat just operated furnace. When we went to disconnect it we found that it was wired with a 4 wire telephone wire.  So my question if you can please answer is which of the four wires do we connect to a furnace only thermostat (since we just need two)?  The wires are red, green, white & black.  Thank you.

Answer
I need the model number of the existing thermostat ,also the manufacturer name and model number of the furnace will greatly assist me, as there are so many different types and models, then I will be able to view the proper wiring diagram for your particular model thermostat. It should be located behind the cover or either on the back. I will be awaiting a reply from you.

Regards, Larry