20 amp fuse failure
I took the trailer to my local dealer.
At first, there was no short at the fuse location where I had blown (melted) several fuses recently. A quandary for the dealer.
After running some checks the dealer discovered a problem behind the furnace.
There is a cable group that is apparently visible if you remove the two drawers from the desk in the back. To work on the bundle you have to remove the desk top and the furnace.
The problem was that the bundle had a ground wire associated with it. There was a group of solder joints right at this location. Also running nearby, but in a separate bundle was the circuit that had been blowing the fuse. Both bundles were wrapped in tape.
Apparently the cable wire `whiskers' in the fuse line had become free after 10 years of service, and had worked their way through the taping around the grounded bundle. Eventually the `whiskers' touched the ground and `POOF'.
However, the situation was such that the ground/short occurred intermittently, explaining why the fuse blew on a camping trip, but was apparently corrected by a simple fuse change. Then, after I had the trailer in for inspection, where there were no problems, fuses blew, apparently movement caused by my towing. Then, when I towed the vehicle back to the dealer the short went away, causing confusion. It was half luck and half skill that the source was eventually found.
The connections were repaired and separation of wires further enhanced by wrapping bundles with a lightweight, corrugated conduit.
The worst situation, intermittent shorts (tied for first with `more than one short').
I also found that the battery is shot, explaining the dimmed lights when running on battery power, a situation I thought might be related to the short.
Hope this helps others diagnose issues.
Mark and Sharlene