ON my carrier V the furnace won't come on unless I request it (Select FURNACE MODE on the remote) Question: Does the FURNACE light on the controller display (Ceiling unit) come on?
Suggestion: Remove the Ceiling cover, Then remove the circuit board (CAREFULLY) and clean (Brush off with a non-metallic brush) Do a general cleaning while you are at it.
IF you have any IR Remotes, then there is another question "Are you pushing a button when this happens".
if so, it may be the two remotes share a code. (Furnace).
IF this does not fix.. then a new control board may be indicated.
YOU MIGHT also have a short in the Furnace wiring.. If this is the case the light for Furnace will NOT come on.
Temp fix: WIth the inside cover off, Look for two BLUE wires on the left (As you face the front of the RV) side of the A/C.. These will connect, usually with wire nuts, to another pair of wires.. Disconnect one of them (Does not matter which) and protect the ends of the wires. This should DISABLE the furnace completly.
Home is where I park it!