How to Turn a Hard Wire Light Fixture into a Plug In Jul 25, 2016How to change a hard wire light fixture into a plug in: Warning: I have basic wiring skills, but I am NOT a certified electrician. This project is completely at your own risk, and I take no responsibility for any mishaps you may have as a result of this tutorial. Trailer Light Plug Wiring | etrailer Quickly and easily connect your towed car's lighting system to your RV to activate the signal lights required for towing. This custom harness plugs directly into your vehicle's existing Or you could just plug in the TrailerMate wiring harness. This custom-fit system plugs into your vehicle's existing wiring harness, which is located behind your car's tail light assemblies.