Furnace?

I would look for a short possibly caused by a rodent chewing the wires. You will need to remove the furnace from the TT to see what is going on. Not too bad once you have done it. You can run the furnace with it removed just shut off the propane. They generally will try to start and the blower comes on then it will shut down if it does not light by the 2nd or 3rd attempt. At any rate you have enough time to figure out what is going on. If it shuts off within a couple of seconds look for a short. If it seems to try to run then fuse blows look for what is keeping the fan from turning. Make sure the casing is sealed when you put it back together there can be some air leaks around the flimsy assy. Some duct tape to seal any air escape.

+1 to pull the furnace for a bench test. At least get in and verify the fan turns freely.

Thanks for all the response. I am going to follow up on all the suggestions this afternoon, starting with the least evasive. I'll let you know how it goes.

Andy

If it is an Atwood furnace, you pretty much need to pull the furnace out and separate the exhaust piping to get at the blower. I recently had to do this because mine filled up with rain water from an improperly installed exhaust vent. The blower is kind of tucked up inside the furnace housing so a wire shoved through the exhaust will do little to clear anything out.

All of the above.
I think something is not so cozy with the motor.
Being you are NOT hearing anything when you attempt to fire it up and the fuse blows from the start, i suspect the motor/fan being restricted somehow.
The fan is not spinning , being restricted by insect nest or a bad wire touching something metal grounding it out or just dirt on the shaft to prevent it from spinning.
Open up your furnace so you get a visual on the motor/fan, spray the shaft, try to spin it by hand. It should spin freely.
Then take it from there if need be, but you will probably need some tech help for electrical testing.

Before you check for wasps nests in the two ports on the outside, you may wish to explore the electrical path to the furnace. A meter will be necesary and some non-advanced electrical knowledge. It could be something as simple as a loose wire in the thermostat creating a short circuit to a failed connector to the furnace's circuit board to a seized blower motor.

Chris Bryant, a member here and an RV tech, offers service manuals on his website. The service manuals have troubleshooting sections to diagnose common faults. Bryant RV service manuals

make model of rv is meaningless. tell us make model of furnace. Suburban, or Atwood? How accessible?

That's what I'm hearing. Can I just run a wire into the furnace exhaust vent?

Wasp, or Mud Daubers, (what ever you like to call them) love to build nest in these RV furnaces.

No I haven't check for that, not exactly sure where to look. And no noise coming from the furnace. It's a 2012 Kingsport by Gulfstream, how to I access the furnace, blower?