Originally Posted by Borrego Dave
Bob, this is the kind of question that can receive many answers but without a pic of the vent for us to go by..........pretty much guesses. It's happened in the past and none of our answers were correct after we saw a pic
BTW, welcome to FGRV.
Photos do help, which is why I used the posters description of the location of the vent they were inquiring about as its being just behind the right wheel well and then did an image search of the Trillium
4500 trailers to see what purpose for a vent was in that location.
I would guess that furnace was an upgrade option installed at time of purchase Not at all unusual to see this being done with cars coming out of the factory having dealer installed options at the time of purchase. The Campster
I own did not have a furnace but they were available as an upgrade so some Campster
do have them.