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A lot of trailers use a 7-way plug, but many vehicles only have a 4-way. This adapter bridges that gap. It plugs right into your existing 4-flat and gives you a 7-way RV blade plus an extra 4-way outlet. That means your trailer lights—running, turn, and brake—work instantly, no splicing or rewiring needed.
If you want to power trailer brakes or charge a trailer battery, this adapter already has the leads for it. The blue wire connects to a brake controller, the black wire runs to the battery for 12V power, and the yellow wire supports reverse lights. The white wire grounds to the frame for a solid connection. It’s a simple way to upgrade when you’re ready to go all-in with 7-way functions.
For setups using the Curt Echo wireless controller, this adapter is a natural fit. You don’t need to run the blue brake wire since the Echo handles that through the 7-way. Just connect the 12V power line and ground, and you’re set. It’s one of the easiest paths to a clean wireless brake controller install.
The built-in 12-gauge power wire delivers reliable current for trailer accessories. When paired with a proper circuit breaker—like a 30- or 40-amp—it keeps your setup safe while running lights, charging a trailer battery, or powering accessories such as lift-assist bike racks. It’s built for consistent performance and simple hookup.
Customer Satisfaction Score:
97% were satisfied with this product
3% of customers were not satisfied
Ratings & Reviews
Perfect fit. Works great.
Good product overall, installed on my 2016 Volkswagen Golf to tow a 13' Scamp fiberglass trailer. Although do be attentive, as other reviews have stated, that using all the functions of the 7-pin connector (electric brakes on the trailer) may require extra work. In my case, it required running an extra lead from the car battery with a fuse in line. I was was able to run it through the body of the vehicle, although I gather it's also possible to run it under the entire vehicle. Just something to be aware of; as my first time towing anything, it was a learning curve to understand how to put it all together.
Your site us very helpfull for information and support and i reallt apreciate etrailer for all tge purpose.good product ,help support,and fait delivery even heure in Canada.
Tgank to all of your team.i am presently installons the controller on my car after the installation i Will feed about how it work.
Have a nice day
Luc
7/30/2023
Very well great product,goid brake controll ,smooth,ibreally like the way it work,and Allo it take juste à small place under dash for me 10 star a grest product
Luc
7/30/2023
Great product the curt7pin with the 4 pin on the side really helpfull for installation good product ,to be sure keeping moisture away in the connector i Also use electric compound grease in it to prevent corrosion and still very good no connection problem yet even with the kind of weather we have here up North in Quebe crain ,snow,..good product well made.
Easy install. Easy videos to reference. Support knows what they are doing.
Sold etrailer customer for life ??
Victoria H.
3/14/2025
Thanks Victor! I'm glad the videos were valuable to you. We enjoy being your go-to!
Well made.
High quality materials and components.
I’m very happy with the help I received from E-trailer but I wished that I was told that I would need 10 gauge wire for the E150 van I was working on. Believe it or not it was very difficult to find 10 gauge wire that is double jacketed. It would have been a bigger sale if you added twenty feet of your wire and I would not have needed to spend the time to get the wire.
I mounted this on our travel trailer so I could use a 4 pin flat plug to connect to the tow vehicle. Works great
Simple install with excellent instructi ons.
On time and the Customer Service is the best I have ever seen!
Very simple and straight forward to ins tall.
Nice sealed unit
Needed to slightly modify the bracket clearance holes to have the plastic holes line up properly and fit cleanly. Not a big deal but someone else may have struggled with that if they expected a simple install.
So far, so good. Haven't installed it yet, but have installed similar one on another vehicle. Have to find good path for the power wire up to the battery.
Robert
7/2/2025
After finding good wire path up to engine bay, it went smoothly. Great to have noth 4 and 7 pole connections available.
Your company makes everything easy to i nstall.
Easily mounted on the platform on the hitch.
Wiring was easily.
The pictures show the harness 6 months after installation. Due to steep driveways and my wife’s driving; it got bent from its 90° angle. Despite the damage, the harness still works correctly and reliably. 10/10 would buy again…may have to if wife keeps driving.
I used this on my 2017 RAV4. This harness provides me the flexibility of using flat-4 or a 7 way connector for towing flexibility. The RAV4 is a small tow vehicle and I like the added security of electric brakes even on lighter single axle trailers which the 7 way allows. I plugged this adapter into the flat-4 connector provided by the "T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector Item # 118578" and used heat shrink tubing around the crimp connectors for the brake controller wires to keep moisture out.
It worked the first time. The fuse sockets on the panel aren't numbered and the photo with the arrows pointing to the sockets on the fuse panel could use some enlargement. However two of the sockets in the panel didn't have contact tabs in them so I knew where not to plug the fuses in.
Installed Redarc brake controller in a Subaru Outback. Instruction clear, and for advanced DIY a two hour job to complete wiring to 7 pin connector.
This was very plug and play. As always mounting is usually the tricky part from one install to another from my experience. I was able to mount mine on my Jeeps factory bumper via some larger holes that were in the bottom of the bumper. I used some fender washers an a metal backing plate for my particular install.
Heather A.
2/19/2025
Hey James! The bracket looks great! The photo really helps other customers if the same Jeep as you. Thanks for taking the time to send it.
Easy install. The 4 pin connector is not great. It's a notch and the pin falls off when I try to plug in a 4 pin trailer plug. The 4 pin notch is a bad design to me.
Installed directly onto an aftermarket Curt hitch receiver, 2018 Nissan Frontier. Everything worked great.
I do have a complaint- not a huge deal: The additional 4-pin connector is meant to sit within a slot on the bracket, but there is nothing holding it there. I wound up using a long zip-tie around it and the body of the 7-pin plug to keep it in place.
I just installed this on my 2015 Volvo XC70. I also used the Curt XC70 plug and Play for wire kit. I watch two of etrailers excellent insulation videos. Installing the hitch and both the wiring products took me around 3.5 hours. I think Curt products are great and they are reasonably priced! e-Trailer makes your DIY installations easy. You just need to take your time when removing interior panels and double check your work. I used Volvo's torque specs for the bumper parts when I installed the hitch. E-trailer doesn't stop with just hitches and wiring solutions, they have just about anything you need to load and haul overhead or behind safely. What about performance? E-trailers got you covered. If you get in a jam during the insulation, don't fret or worry, call the text at e-trailer and they'll walk you through it. I want to thank E trailer and their professional staff for helping me with my truck and auto towing and lighting solution for over 10 years now!
Roger
5/9/2025
I love it.
Easy to install but the 4 way wire harness just slides into the metal mount, where it also slides out of. Use of a few wire ties to hold it back to the main wire bundle solves that problem but for the price, you shouldnt have to do that.
Mike L.
8/27/2026
I've used black RTV such as # LT37467 for that in the past, and it worked very well.
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Nick S.
9/15/2025
That is great to hear Jeff! Are you towing anything crazy with this??