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Wiring up a trailer doesn’t have to mean cutting into factory wires. This Curt T-Connector harness plugs directly into the vehicle’s existing wiring to create a 4-flat trailer connector. It’s a simple plug-and-play setup that keeps the factory wiring intact and avoids the headaches of tracing or splicing wires.
The harness tucks neatly behind interior panels, keeping everything out of sight and protected from the elements. That hidden connection not only looks clean but also helps prevent damage or corrosion since nothing is hanging under the vehicle.
Once connected, you get a 4-pole flat connector that powers your trailer’s running lights, brake lights, and turn signals. It’s the standard connector used for light-duty trailers, making it easy to hook up and go whenever you need to tow.
Even if your vehicle didn’t come with a factory tow package, this harness has you covered. The integrated converter handles the signal translation needed for trailer lighting, so everything works correctly right out of the box—no extra modules or rewiring required.
Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.
Jeff: Hello, everybody. This is Jeff at etrailer.com. Today, we're going to take a look at this CURT T-connector vehicle wiring harness with the four-way flat trailer connector. Now this is a custom-fit part. It is designed to fit the 2019 Mazda3 vehicles. And on a custom-fit part like this, I always like to recommend for you to go to our website, use the fit guide.
Put in your year and model vehicle and it'll show if this'll work for your application.Now, this harness will provide this four-way flat trailer connector at the back of your vehicle to power your trailer's signal lights. And it is compatible with five-pole, six-pole and seven-pole adapters that we do sell separately on our website.This will connect very quickly and easily. Basically you just locate your connection points, which are behind the taillights of your vehicle. Plug in these T-connectors, one on the driver's side, one on the passenger's side. Ground your white wire, then run your black power wire to your vehicle's battery.Now it does include this black box here, which is your tail light converter.
This is to ensure that your vehicle's wiring will match that of your trailer. It is a powered module. That's why it connects directly to your vehicle's battery. And they do that to avoid overloading your vehicle's electrical system.This converter is constructed using SMT technology, which is surface-mount technology. Gives you a more consistent, reliable performance.
It will maximize your trailer light yield and intensity, while producing minimal heat. It also ensures a nice, superior operation in any rough road conditions.Now, this kit also comes with this nice rubber dust cap for your four-way. And what's nice about that, you can just attach it to the four-way and you can leave it on there if you want. And then when you're not plugged into your trailer, just take your dust cap, put it over the terminals and it'll protect them from any damage or from the elements.A few specs on this harness. The maximum amperage for the stop and turn light circuit is five amps per circuit.
Taillights is 7.5 amps per circuit. It does come with everything shown here on the table. It comes with a nice set of detailed instructions that will describe how everything installs and pictures of where they connect.But just briefly to go through the connections on these. And what you'll do again, is go to the rear of your vehicle, access behind the taillights. And you'll probably want to start on the driver's side and take the wire that has the yellow and red in it. That's for the driver's side. Unplug your harness, plug this T-connector in line there.And then what you'll do is take the other T-connector with the green wire, that's for your passenger side. Run this length of wire over to the passenger side, plug this in behind the taillights. And then this converter box, it does have a little weight to it. So you do want to attach that to a good flat surface so it doesn't bounce around. They do have a tab on it with a hole which you can put a screw in if you want. But they also give you this nice double-sided tape that you can put on there and attach it down that way.Run this bonded wire with the four-way out towards the trailer. And then you'll have two remaining wires. The white wire, you can see has an eyelet on it. That needs to connect to a good clean ground if there's one nearby. If not, they do include this grounding screw that you can make your own ground. And then the remaining wire is your power wire. This needs to run to the vehicle's battery in the front. They do give you this length of wiring and the connectors to do that.So if you take a butt connector, connect it to one end of this length of wire, run it all the way to the front. Now you don't want to run this directly to the battery. You want to run it through the inline fuse holder. Take the other butt connector, connect it to one side of the fuse holder, just like that.And then on the other side, take the eyelet connector, attach that, and then connect it to the battery. Pop open the fuse holder, take the included 15 amp fuse. Just install it into the fuse holder, just like that, put your cap on and your system's all ready to go. If you notice they do include some extra cable ties. That'll help take up any slack in any of the wiring. But that should do it for the review on this CURT T-connector vehicle wiring harness with the four-way flat trailer connector.
Customer Satisfaction Score:
95% were satisfied with this product
5% of customers were not satisfied
Ratings & Reviews
Jimmy O.
9/8/2025
The wiring harness has held up even a year after buying it. The lights dont flicker and the product is good quality.
Info for this part was:
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Jon
4/8/2025
Works well no major issues. However Corrosion is an issue with this hitch. Paint has been flaking away where the paint was chipped and is rusting, even though I had painted it. I will use a wire brush on it and some more rustoleum and see how it works out. It is surface rust and not a danger to integrity.