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Trailer 4pin wiring

323 Views 8 Replies 4 Participants Last post by  GlenC44
Ok, I scrolled all the way back to the first post here and didn’t find it.

I’m looking to wire a 4 pin trailer plug on our 2016, any knowledge out there?

I don’t need trailer brakes, all the threads I found were trailer brake related.


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Do you have the trailer hitch and 7 pin connection on the hitch?
Trailer hitch, yes (after market) zero wiring and it does not have factory tow package.

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You are going to need the control box plus programming and the wiring harness for the 7 pin. Parts are listed in the oem hitch thread.
there is this wire harness which works with sensors and you don't cut or splice the wires which can spell doom.
i believe someone here installed that but can't remember which of the numerous trailer threads.
This is the thread that would include part numbers for the oem wiring components.

Thanks for all the info and links. I’ll forgo this.

I have 2 10-15k trailers and a F250.

I added a hitch to the Metris for a bike rack and recently picked up a small single axle (no brakes) utility trailer for my sons lawn mowing business.

I was gonna add a 4 pin for that trailer, so I didn’t have to take the truck, however don’t think it’s worth the hassle.

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Yea, it's not free. The van has features tied to having a trailer connected so it's worth having if you pull a trailer. Seems like the parts can be had for a couple hundred maybe. Routing the harness under the bumper cover is probably the hardest part. But yea, takes some effort.
I added a MB 7 pin wire harness and it needs the interface module installed to the passenger rear behind the tire jack in my 2016 passenger Metris. I didn’t have any programming done. Having said that my Metris doesn’t have any lane warning or close vehicle warning. Those features might make problems without the programming.
After installing the wiring and module I used a 7pin to flat 4 pin conversion and the lights worked fine.
My camper trailer has brakes and that creates a whole new set of problems. First is when you plug in the trailer 7pin it can blow the Metris fuse for the trailer battery pin. Second the Metris accessory battery is the one used to power the trailer battery and camper interior. The accessory battery only charges when coasting. Therefore you eventually have a dead trailer, and accessory battery, and no trailer brakes. I left the fuse blown and ran a separate 10 gauge wire from the starter battery, through a breaker and relay directly to a battery charge controller that I had for my solar panels. This isolated the starter battery from the trailer battery and accessories battery. The charge controller prevents over current situations and keeps the trailer battery charged to operate the camper and trailer brakes.
Having said all this I would not encourage anyone to do what I did. I sort of got sucked into it one problem after another and didn’t give up until it all worked.
Good luck
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