I was having real trouble with the gauge-cluster illumination lights. My car didn't have a dimmer switch, so I was going to just rewire it without one. But after doing so I kept blowing fuses trying to run a parallel circuit so I had to cut into the gauge-harness and route a new isolated circuit to feed power to the gauge lights.
And I thought attaching the speedo cable in the FC was hard. FB's are worse! lol
Since I won't be using the spot for the dimmer switch, I've decided to run toggle switches there for foglights and auxiliary driving lights. Luckily for me, FC toggle-light switches fit perfectly. Always cool to find a use for another FC part in my collection.
I bet your undertray doesn't look this clean
