No heat

Typically RV furnaces don't like to not be used for a long time. Too many things can happen.
1. The green ground wire that is screwed to the furnace metal gets loose or corroded. Loosen and tighten it.
2. Mud daubers build nests inside the furnace. This either clogs the blower air path, or worse builds up on the sail switch. Maybe blow some compressed air through the outlet to clear it out and hope that helps.
3. There is a control circuit board with a connector on it. Sometimes the connections on that board get corroded. Pull the connector off and on several times and see if that solves the problem.
4. Probably not the case, but also possible the gas valve is stuck.
5. The heat sensor rod may not be clean and is not sending an igniter signal to the gas valve.

I'm sure others will have additional ideas.

There is a "sail switch" that looks for airflow through the unit. If it is stuck (or bad), it will not allow the gas to turn on.

https://www.youtube.com/watch?v=-g3_Y7MqChE

garyemunson wrote:
There is a "sail switch" that looks for airflow through the unit. If it is stuck (or bad), it will not allow the gas to turn on.

Or if something is blocking the air flow, the Sail Switch is doing it's job.

Dusty

At our age (81) we would call the nearest available mobile RV tech. About a year ago we had to replace the gas valve in our furnace.

The fan comes on first, if it's moving enough air then you should hear the igniter clicking. Is it trying to light?

Stink bugs. Probably dead now. Flippin' things get in everywhere, and one crawling into the burner tube of your furnace, water heater, grill, or other propane appliance will screw up the burn and result in just this problem. On the one hand, pulling the burner assembly out and blowing the bug(s) out is a cheap fix. On the other hand, it's a pain in the neck for sure. So before you fuss about the other issues above, look for stink bugs in the burner.

Sounds like no propane.

The bad news is, you have to pull the complete furnace to troubleshoot and fix on your model furnace. The other bad news is, when you pull the furnace, odds are the jostling will reset the hi limit switch IF IT WAS the cause of no ignition. Sooo, When I have this type problem with a no access furnace, I take a rubber mallet and sharply pound on the inside burner casing area. Then try to restart the furnace. IF it then lights and stays lit, I pull the furnace and replace the Hi limit switch as it is sticking OPEN. Regardless, with a non accessable furnace when I pull for repair, I ALWAYS replace the Hi limit regardless of any other bad part is the problem. The Hi limit is not that expensive and cheap insurance to prevent a future problem caused by a intermittent hi limit switch. Doug

Our furness would not work in the morning when we first got up but would fire up a few hours latter when I was out trying to fix it. All the other propane stuff worked fine. Then the range started having a low flame so I replaced the propane regalator, now the furness works all the time.