Why Does Trailer Wiring Require Black Power Wire to The Battery

Updated 09/05/2019 | Published 09/04/2019

Question:

I have wired quite a few vehicles by just tapping in with the more basic four to three harness, and making sure all trailer lights were LED. I owned one such vehicle for ten years, and a couple others for at least two years. As long as I tow only LED equipped trailers, no problems have appeared. Is there a problem you see? Vehicles that require a wire to battery

asked by: Ben A

Expert Reply:

Not all vehicles can handle the additional amperage draw of trailer lights so the wiring harness requires a power wire to the battery. Some vehicles do have higher rated circuits that can handle powering the trailer lights without a power wire to the battery. You may not have an issue since your lights are LED and draw very little power but If the custom wiring harness available for your vehicle has a black power wire I do recommend to attach it to the battery. Trailer wiring manufacturers design and test the wiring on specific vehicles and have determined the electric systems in those vehicles cannot handle the extra load. Also newer vehicles have more delicate and intricate electrical systems so I do not recommend splicing in if you do not have to.

expert reply by: Heather A