There may be a switch next to the door that you push to keep the step open when parked, otherwise it will go in & out every time the door is open. If it is working that tells me the fuse is good. I have a similar setup on my Monaco.
You may try to call Holiday Rambler
Their website does have an archive of manuals but it only goes back to 2000, it might be helpful to some extent.
Manuals
Good Luck