failed electrical connection on brakes on one side only
We took our new-to-us 1999 30' Excella to our favorite mechanic to get the brakes checked and bearings packed. He's an excellent mechanic, and has worked on big trailers/brakes before - although not Airstreams.
He said the brakes and bearings were fine, but the brakes were only activating one side - there was no electrical signal to the other side.
He's going to track down the problem, but I thought I'd see if I could get some quick advice to pass on to him as to where he might start.
So, what's the most likely place for a problem? (by the way, he says my plug doesn't fit as snugly into the back of my (new) TV as it should. I'm sure he'll look at that.)