Bluegrass,
What I was saying that I had turned EVERYTHING off, as I have to do with each trailer...can't even anything at all on, and then everything is good. I had the radio on, with the door open while I was plugging the trailer in and ...no lights.
Be clear, I blew the fuse on another trailer, which caused me to realize that it was occuring on my boat, on my sea doos, and on this enclosed trailer. I realized it was only the right side, then realized there was a specifc fuse for it.
Ran that trailer to Sturgis and back with no problems, plugged and unplugged several times with EVERYTHING OFF...and no problems, everything worked.
I picked up a travel trailer on Thursday last week (when I posted) and lo and behold, I left the radio on...no more lights on the right...running/turn/brake...nuttin'.
So, the only way I'm having any luck is by being sure absolutely everything is shut off. I'm certain it's not 4 different trailers having the same issue. It's simply that the damn truck is wired poorly and there is enough draw "somehow" to cause this fuse to blow. I will be trying a circuit breaker this week...maybe that will be my fix for now, but beyond that, it's a pretty sad thing to be able to find this same problem occurring all over the internet without Ford figuring the fix.
I did check wiring at the harness and plug...everything was working fine on the harness and at the plug when the fuse was new.