I read this thread with interest. It is an example of the rules:
Write everything down
Don't ever trust to memory
Measure twice before cutting once.
Working with electrical
circuits for a local aircraft company, I learned that you never trust anyone else's work, always double check. Electrical
things go together easily, it is when you turn the current on that you discover you have problems. "Houston, we have a problem." Check again.
I was told when I took delivery of my trailer, to not worry when stopping for an hour or two, but for parking overnight, always unplug the trailer or it will draw the tug battery
As far as dragging the plug end, I have two systems:
1 - I physically attach the plug to the trailer
2 - My Brake controller will not show "c" if the trailer is not hooked up.