How to Build a Wiring Harness - Muscle Car DIY Jun 27, 2015Route the switch harness from the relays to the switch location, properly anchoring this along the way. Step 8: Route the wiring toward the kick panel areas of the vehicle, being sure to anchor it up high as you go. DIY Wiring Harness - Buggies Gone Wild Feb 26, 2011DIY Wiring Harness. i'm building my own wiring harness for lights and such and thought i'd share the progress the community. i started out with just fog lights, a relay, a switch and a 12v battery. i would eventually like to make the cart street legal so i've since cut in some factory CC front lights and aftermarket LED tail lights.