Why Does Power Wire of Trailer Wiring for 2011 Mazda CX-9 Have to Run to Battery Directly

Updated 05/26/2020 | Published 10/18/2016

Question:

Considering one of your wiring harness for my 2011 CX-9 Mazda Found the review below and had a question. Snaps in. Well built. I tapped into the 12v power from the rear accessory outlet. I found that this is live all the time and has its own 15 amp fuse. Should work just fine and made the installation MUCH easier and cleaner. 57028 I wonder how I can tell if I can tap into the 12v power at the rear accessory outlet. It would be nice to be able to do so and avoid running the wire all the way up the car to the battery. Can you tell me how one could do this?

asked by: Ceci P

Helpful Expert Reply:

If you were to run the power wire of the Curt Vehicle Wiring # 56016 to anywhere but the positive post of your vehicle battery you would void the warranty of the harness and could potentially damage the wiring of your CX-9 in the event of a short on the trailer wiring.

The purpose of the battery wire being run to the battery is so that it bypasses the delicate vehicle wiring and eliminates the potential threat of the trailer wiring damaging the vehicle's wiring. It draws all of the power for the trailer taillights through the battery wire. That is why you do want to run it to the vehicle battery.

I attached an FAQ article on routing the power wire for you to check out as well.

expert reply by: Jameson C

Bill S.

5/23/2020

why does the mazda require a powered wiring harness, but on my 2000 Dodge Dakota, it just plugged into the tail light plugs?

Chris R.

5/26/2020

Some vehicles have more delicate factory wiring than others. Typically when a power wire is required, it's because the factory wiring for the tail light circuits simply don't provide enough power on their own to also activate trailer lights, so direct connection to the battery is needed.