Electrical gremlins

I just bought this truck (without a warranty of course) and when someone uses the passenger side lumbar,it makes the inside lights come on and the dash and headlights dim. Any suggestions?

Come on y'all, you can't tell me nobody knows anything about this. You guys are a heck of alot more knowledgeable than the shops around here. A little help would be greatly appreciated.

That the headlights dim, usually means that there's a short when using the lumbar. That the interior lights come on would mean the the trigger wire to the interior lights is being shorted to ground. I don't see how these two problems would occur unless you have a short in the harness and also a bad lumbar switch.

First thing I would do is unbolt the pasenger seat and see any part of the problem goes away. If it does, you know that the harness under the seat is crushed.