standguard

Hi. Looking to buy a used 2018 XLT this weekend. It only has a 4 pin wire for towing. I know I need 7 pin. How can this be done?

jp360cj

What are you planning on towing? If you need the 7 pin plug, chances are the non tow package truck isn't going to cut it for you.

standguard

smokeywren

Hi, standguard, and welcome to our campfire.

You'd save yourself a lot of headaches and frustration if you bought an F-150 that includes the factory towing package 53A, or better yet the max towing pkg 53C.

But if you want to convert your 4-pin trailer pin to a 7-pin, it can be done. If you're not an automotive wiring guru, then I'd have my Ford dealer's service department do the work, using Ford OEM parts..

As a minimum. you need to replace the wiring harness from near the rear axle to the rear bumper with the 7-pin wiring harness and plug. And if your truck has the plug for the trailer brake controller behind the cubby hole in the dash, then you need to install the fuses and relays in the fuse box and power distribution box that are not already installed but mentioned in the fuse/relay charts in the Owner's Guide as having anything to do with a trailer or TT. Trailer brake control, TT battery charge, etc.

If your truck does not have the plug behind the cubby hole to plug in the trailer brake controller, then you need to install the fuses and relays mentioned above, plus you have a major task ahead to replace that part of the wiring harness that includes the plug behind the dash for trailer brake controller.

Then you have to buy a good trailer brake controller so the trailer brakes will work. I would insist on the OEM Ford integrated trailer brake controller (ITBC) because it's not expensive and it's the best on the market, but you can get by with an aftermarket controller.

standguard

Thank you for the thorough response. Would you mind helping me with a couple additional questions?

So if I understand you correctly simply disconnect at the rear axle and adding a 7 pin will not add the wire that brings power to the trailer brakes. You need something that is wired from the fuses and relays all the way back to the trailer hitch connector.

If you buy a truck with the factory towing package do you still need a brake controller?

smokeywren

Probably a fair statement if the F-150 does not already have the wire behind the dash for the trailer brake controller. That indicates that the wiring harness is not set up for a 7-pin plug.

But if your F-150 has the plug for the trailer brake controller behind the dash, then if you replace the 4-pin wiring harness with the 7-pin wiring harness at the back of the truck, and install the required relays and fuses in the fuse box (passenger's footwell) and power distribution box (under the hood near the radiator), then when you install the trailer brake controller all 7 pins should work. All 7 wires are already there from the fuse box to the rear axle. 1 pin is for ground wire. 3 pins are for trailer lights. 1 pin is trailer brake controller. 1 pin is trailer battery charge. And one pin is however it's wired at the fuse box for either backup lights on the trailer, or extra 12-volt hot wire for flood lights or whatever you decide to use it for.

There are two different towing packages. With the 53A "regular" towing pkg the integrated trailer brake controller (ITBC) is optional but not included. With the 53C Maximum tow package, the ITBC is part of the max tow package. Max tow requires the 3.5L EcoBoost engine, and also includes the 36-gallon gas tank, upgraded front stabilize bar, and slightly stronger receiver hitch Ford calls an upgraded rear bumper.

The frame of the rear bumper has three parts, left, right, and center. On F-150s that have a factory receiver hitch, the center part of the rear bumper frame includes the receiver hitch. That center part of the rear bumper is available in three different configurations (part numbers); without a receiver, with the 53A or 53B receiver, or with the max tow receiver. So I guess that's why Ford calls the bumper with the max tow receiver an "upgraded rear bumper".

GCTruck

Ha! In the middle of the same project! Bought a 2018 XLT 4x4 w/4 pin myself!
If you haven't bought it yet, first thing to check is the fuse box. Apparently sometimes Ford wired the 2018's with the necessary fuse connectors, and sometimes it didn't! [You need to check the # 24 fuse position for a 30 amp fuse and/or to be sure the metal connectors show in that position so it can accept the furse. -- More on that in some other posts.]
If you got one of the "bad" fuse boxes -- like I did -- you either replace the box or you create a new hot lead from the batter post, through a breaker, to . . . another location. I wanted to stay OEM so I bought a new box and am putting it in today.
The rest of the upgrade involves
-buy/install OEM TBC (should be plug-n-play, but apparently sometimes there is a lead that is not active)
-buy/install 7/4-pole connector (OEM style, cut out for mount near license plate)
-buy/install new wiring harness (or make your own)
-activate the TBC (at your dealer, or by using Forscan and doing it yourself)
I intend to do something more complete with part numbers when I have finished this project, but that will give you some idea of what's involved.

old_programmer

From 2015 on there is no relay as the 12V aux line is directly driven from a power control module in the truck. It is enabled at the same time an OEM TBC is enabled in the truck software. If you use an after market TBC I do not believe you will be able to use the installed wiring harness for the aux line. In this case you would need to install your own aux line, relay and fuses.