Originally Posted by Canucklehead
When I wired ours up I was concerned about drilling into the wall to tap into the wiring harness, so instead I tapped into the junction box near the pin box and fished a wire through the front storage compartment and out the propane cylinder cabinet. I used outdoor rated wire and ran it along the frame rail to the bumper. No need to drill anything (other than the wire clamps).
If you pull your taillight assembly off the wall, then you can run a stiff wire up, or down, which ever way you want to do it. Then you will have your wire on the bottom side of the trailer, ready to hook the pig tail to. There is no need to drill a hole in the trailer wall.