Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
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2010 Ford Flex
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2010 Ford Flex
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Running wires and cutting into factory circuits can be a headache. This Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector uses a plug-in design that connects directly behind the tail lights. There’s no need to cut or splice, so installation stays clean and simple. Once it’s plugged in, the 4-flat gives you running lights, turn signals, and brake lights ready for towing.
Modern vehicles have sensitive wiring that can’t handle extra trailer load. This harness includes a powered converter that draws power directly from the battery through an inline fuse. That setup isolates the trailer wiring from the vehicle’s taillight circuits, protecting them from shorts or overloads. It’s a dependable way to keep both vehicle and trailer lighting working right.
With its direct battery lead and solid ground connection, this harness helps prevent dim lights, blown fuses, and false signals caused by weak or shared grounds. It keeps voltage steady across all circuits so your trailer lights stay bright and consistent when you hit the brakes or turn signals.
The 4-flat plug gives you everything you need for basic trailer lighting—running, brake, and turn signals—all in one standard connection. It’s the common setup for small utility trailers, campers, and boat trailers. Just plug it in and you’re good to go for the next trip.
Customer Satisfaction Score:
95% were satisfied with this product
5% of customers were not satisfied
Ratings & Reviews
Instructions along with video made the installation procedure straight forward. Removing or loosening plastic trim not difficult, however takes a bit of time to be careful when reinstalling and making sure everything lines back up like it should. I have a 2011 Ford Edge and there is a perfect flat spot about the size of the control box under the driver side taillight, almost like it was made for it! Running the black wire back up to the battery took me some time as I was doing by myself without a lift. I had to remove a protective shield underneath the drivers side of the vehicle. This gave me easy access to mounting points for the wire zip ties. Used a thick wire to pull black wire up to battery. Installed inline fuse. Connected to battery. Took me 2 hours to install. Worked perfectly first time with trailer!
The box arrived quickly, contents in perfect condition. The hitch was perfectly engineered to fit our Ford making the assembly easy and required just basic tools. Your company's wire pull through gadget is very clever, easy to use and solve the huge problem of getting the fasteners in place. We have used the trailer a dozen times and it sure comes in handy. The electric harness took the most time since I did not want to have loose wires showing anywhere. I would, without hesitancy, recommend etrailer's parts.
My Curt T-Connector wiring harness arrived sooner than promised - Thanks etrailer! The installation instructions and video on etrailer were a big help. The instructions that come with the unit do not include some of the detail/tips that the etrailer video does. I took my time and was very satisfied with the finished installation. My trailer has LED lights and this adapter works just fine with them.
The installation goes pretty much as shown in the video. Here's a couple of tips from my installation:
Getting the taillights out wasn't as easy as the video shows. I used the handle of a flat tablespoon and slipped it between the front of the taillight lens and bodywork. Pry back toward the rear of the car to help loosen the taillight from the two locating pins. This prevents marring the body paint and helps you pull straight back on the taillight. They come out with a scary-sounding "pop".
I found that it was not necessary to remove the rear trim panel to get the spare tire compartment bins out. I just lifted up the front of the bins while pulling back on the trim panel and the bins came out easily. I also found that it was not necessary to loosen the side panels to feed the adapter plugs up to the taillight wire opening. I was able to reach these through the opening near the bottom. The passenger side was a little tight, but I was able to wiggle the adaptor plugs through.
The video shows that you cut through the taillight wiring grommet from the outside to the center to install the adaptor wires. I was worried about the grommet not sealing properly on re-installation. I cut a slit in the grommet from the center to close to the outside edge - but not cutting through the ring that seals against the bodywork. I was able to stretch the slit over the adaptor plugs and wires while leaving the outer sealing ring intact. I used the included silicone sealant to seal up the slit where the adaptor wires come through. I'm very comfortable that I have a positive seal that will not leak.
I decided not to route the flat plug wires out through the spare tire compartment grommet as shown in the video. Instead, I keep the flat plug wiring in the spare tire compartment (when not in use) and route it out beneath the hatch door when I want to use the trailer. The installation video for the Tekonsha T-One adaptor shows this method. Seems to work just fine.
Other than these differences, the installation went exactly as shown in the video. The adaptor has been working great with no issues. Thanks etrailer!
Fits and works great. No issues with any electrical.
Came with everything you need. Good quality wire and accessories. Needed it because I got a good deal on vehicle, but it had no hitch or wiring for one.
With the instructions provided, including the associated video, the installation was really easy, and all of the components were top quality.
However, the first time we hooked up a camper we had just driven 4 hours to pick up, the brakes defaulted to "on", and we could not drive with the brake controller hooked up.
Now the best part..... An etrailer technician took our call immediately, and had the background knowledge to know that some Nissan Xterras had factory wiring reversed, which required the corresponding kit wiring to be reversed. After we did so, the system worked perfectly. I would not have figured that out in a million years!!!!!
Great product made even better by fantastic service!!! Customer for life.....
I purchased this wiring kit for my '13 Ford Edge along with a Curt hitch and an additional wiring kit to get electric brake control with a 7-blade connector.
This kit interfaces with the factory wiring by sensing which bulbs are being illuminated without actually being wired together with the 4 pin connector. The well written instructions made the job easy. I ran the 12 volt power wire up to the front of the SUV when I ran the cable for the electric brake controller.
The 4 pin connector simply plugs into the 7-blade connector in the other wiring kit.
Product worked just fine, once installed. Running the power lead all the way to the battery is an extra chore, when others only in the past only required a t-connection at the tail light. There was no instruction or tip on how difficult it was to route the t-connections through the tight grommet, down inside the body and into the spare tire area.
Laura E.
11/10/2016
We are glad you mentioned the installation of the hot lead, Andrew. While it is an additional and sometimes cumbersome step, the hot lead is actually a way to protect the taillight circuits of the vehicle. It allows the trailer taillights to be activated by drawing the power for them directly from the battery and not from the taillights of the vehicle. This actually protects your vehicle wiring and is the safest and best way to do it.
Easy all around !
Very happy thus far with etrailer.com and their delivery of the purchased products. Cost and quality are very good. Haven't installed it yet , but if it goes as easily as shown in the installation videos, I will be VERY satisfied.
Mike V.
4/26/2016
Thanks for reaching out and checking back with me. I love it. If I need to buy another one in the future I will be buying it through you all.
Professional product. Install was medium difficulty but had good results. The flat 4 pin receiver just dangles from around my trailer hitch. Wish a clip or bracket to mount it could have been included. Would have made a neater looking install.
Jerry W.
8/3/2018
the trailer wiring kit is doing just fine. Very pleased. Thanks
I received this harness today and installed it in 45 minutes, on my lunch break. I have an Edge Limited with electric tailgate lift and base speaker in the rear, so both my right and left side were supposed to be difficult to access. At least according to the other reviews. The left side, the side with the electric lift gate arm, was done in this manner. I removed the tail light and pulled out the grommet from the outside, then fed the wiring up the inside of the trunk with my arm and used my other hand from the grommet hole to feel for the wiring. Once I felt it, I pulled it through. The other side was a bit more tricky. Once the outer trim is removed, the speaker cabinet is still in the way. But, I found 3 10mm bolts. I loosened them (they don't need to be fully removed) and that gave me enough room to pull the cabinet away from the wall and slide the wiring up and out of the grommet hole. Piece of cake. I then took the positive battery wiring and fed it through starting from the battery. Go backwards, it's much easier. Great kit and was a snap to install.
Tom L.
9/14/2016
Great harness and install instructions
Very happy with this kit! It had everything that I needed. The double sided tape for the converter didn't stick but other than that I'm pretty impressed. It took me maybe an hour to install. Yhe tricky part was fishing the power wire to the battery. I used electricians fish sticks to get from the back to the front and then through the same hole as the hood latch cable. Had to move the battery too.
I would not ever consider buying tires anywhere else than etrailer. Your 5 star tires,service and follow up are wonderful.
Pretty simple 2 install I love plug n play items
The wiring kit worked great. Pro tip, if you have the power outlet on the LH side, just grab your constant hot there. It's more than sufficient to power the module and you'll already have that panel loose anyway. There is a nice ground back there too. My only complaint is having to put such a large slice in the OEM grommet for the large molex connectors.
Good kit, easy install.
Wiring went in as per the video. The only problems I had were routing the power wire to the battery, but finally found a way, and I had trouble getting the wire connectors crimped enough to hold the wires. Luckily I had extras from previous DIYs.
Steve
5/13/2025
The wiring harness works great. No problems so far. The hitch also works great on my 2012 Edge.
I ordered this item to go with the CURT Class III 2" receiver, it was a breeze to install and looks great. The shipping was AMAZING and showed up as promised... I would recommend the company and site to anyone!
* Quick install Tip if you have the upgraded stereo system as I did the passenger side tail light is a little tight. You can remove the factory subwoofer box and follow the provided instructions from there or if you are "semi-handy" you can cut the (green wire) and insert from the gasket, then simply splice the wire back. I chose the splice option, and everything works beautifully.
I feel like they could've come up with a better way. Not having to run a wire all the way to the battery. That's a bit ridiculous! I bypassed that part and just turn my lights on when using my trailer. They could've tapped into a different power source with the harness instead of a thick wire all the way to the front of the vehicle.
Steven
6/17/2025
Same
Great packaging, fast shipping, good instructional video, good diagrams, good descriptions.
Install was easy, the online video was a great help with each step in the process. Now I can use my trailer for getting lumber for my home projects and yard work.
This harness is exactly what I was looking for. Worked straight out of the box just plug and play.
This went it fairly easy but I do agree with some of the other reviews in regards to feeding the plugs through the existing rubber grommets for the tail lights. It's tight but not too difficult. the kit came with some rubber silicone, so it can be applied to reseal the cut grommet. As far as getting the power wire through the firewall, I removed the battery and made a small hole with a drill bit with an extension and then taped the wire to the bit and pushed it through the grommet.
Victoria H.
2/20/2025
Thank you for your valuable insight and for including photos with your feedback, Lindsey! I know this information will be helpful to some shopping this wiring harness in the future. What are you towing?
2 prior harnesses purchased elsewhere manufactured for the vehicle did not work. I prepped the vehicle for installation. My part arrived and installed in 10 minutes. Works perfectly. GREAT costumer support during ordering. Very patient answering all my question's. Thanks etrailer.
Mike L.
7/14/2026
You're very welcome Duane, I'm happy we could help you out!
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Steven
5/14/2022
So far no problems after a year.