It doesn't look like there is any circuit protection for the furnace system once you leave the off/on switch, if you have one.
RV manufacturers are notorious for not accurately documenting their fuse blocks and breaker panels. My first check would be to pull each fuse, one at a time, and check it. If it's good, move on to the next one, until you've checked all of them.
Here's a link to the service manual for your furnace:
I hopefully attached the wiring diagram for your furnace.