Bad smell when running heat

dead mouse on your plenum.
I really don't know what a plenum is but assume it is the housing enclosing where the flame is, and gets really hot, and if the mouse died on top of it, the mouse gets hot, doesnt burn, but roast and smells. The smell will be blown through the vents.
Is your smell from the vents?
Eventually the smell will burn itself out, like a scented air freshner stick that has expired.
If it is a mouse then you likely have gross mouse droppings and you need to clean it all out. Prepare to take things apart to get to the dropping. Droppings are a health hazard.

My TT has a bad smell from the furnace each time I turn it on. It is caused by dust burning off the the plenum and the plenum itself heating up after it has been setting for awhile. But, it doesn't last after a week of constant use.

One more question- is the ductwork mostly on the inside of the trailer or underneath on the outside typically? There’s an access under my oven but other than that and the obvious vents in the floor, I’m not too keen on the location of things. Thanks!

You may be able to hook up a "crevice tool" to your shop-vac. Good luck!

Thanks everyone! I’m going to give it a shot this week my next off day from work. Hopefully that does the trick!

Also agree on mice infestation. I had same thing on my last trailer. Ended up replacing the ductwork. Not the easiest job in the world, but doable even for novices. I bought a box of dryer vent(the silver foil flexible type). Pulled the old out and put the new in. When I took each vent run off of the furnace I could check somewhat the inside of the furnace where I found some droppings and a partial nest
which I vacuumed out and cleaned the best I could with clorox. Im sure there are some youtube videos for tutorials. The hardest part is the cramped spaces you must work in. Just remember where the old was, and put the new in the same places. You can do it!! The old that I took out went immediately into the trash. Just had a very,very faint odor in the trailer after that. Gary

Few things smell worse than dead mice in the ductwork. :E

Have you found mice droppings in the trailer ?

Mice infestation will leave a permanent unpleasant odor and is exasperated when they take up residency in the ductwork and furnace....I know.

Yes, clean out the duct work. You may be able to inspect much of it with a flashlight and mirror after removing grilles. If you can replace flexible ducts it might be easier than trying to clean them. I hope you don't find a deceased rodent in or around the heating system. Video