I replaced the brakes on my old TT a few years ago. When I really got looking, I noticed that the main wiring harness was only 14 gage wire. While that is enough to handle the amperage seen at the brakes, I wondered about voltage drop. So I re-wired the entire thing with some 10 gage I had. Totally over kill, but...
Problem was I had a short right off the bat.
Fortunately, I was able to borrow a
clamp-on DC amp meter. Using that I was able to quickly locate the source of my problem.
If you don't have one, beware that they are many $$$. If you need to find out DC amperage in a single circuit (or locage a short) and can borrow one from somewhere, they are the bees knees.
Eric