Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
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2020 Mini Cooper
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2020 Mini Cooper
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Running trailer wiring can be a hassle if you have to splice into the factory harness. This Curt T-Connector makes it easy with a plug-in design that connects directly to existing vehicle plugs. No wire cutting, no guesswork—just a clean, hidden install that’s ready for towing lights right away.
Once installed, the 4-flat connector provides all the basics your trailer needs—running lights, turn signals, and brake lights. The built-in powered converter combines separate vehicle circuits into standard trailer light signals so everything works correctly when you hook up.
The included converter box keeps the vehicle’s sensitive electronics safe while sending steady power to the trailer lights. It uses direct 12-volt battery power through a black lead and grounds through a white wire to maintain consistent brightness and reliable operation over time.
If you decide later to add electric brakes or charge a trailer battery, the 4-flat connector from this harness can plug right into a 7-way adapter like part #37185 or #ETBC7. That means you can expand your setup without having to redo the wiring you already installed.
Customer Satisfaction Score:
91% were satisfied with this product
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Ratings & Reviews
Kate F.
11/12/2025
I’m really sorry you’re having trouble with your trailer lights Walter. That’s definitely frustrating, especially after installing a new harness. Most of the time when the lights only work correctly with the headlights on, it turns out to be a ground issue rather than a bad harness. On your 2021 Mazda CX-30 with the Curt 56450, make sure the white ground wire from the module is attached to bare metal inside the left rear cargo area, since that spot is often painted or sealed and can block a good connection. It can help to remove the screw, sand down to clean metal, and reinstall with a star washer. Also check the black power wire running to the battery to be sure the fuse and terminals are clean and tight. Finally, take a look at the trailer’s ground; if it’s weak or corroded, the lights can try to ground through the running lights, which makes them work only when your headlights are on. Please let me know if this fixes the issue.
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Victoria H.
10/28/2024
Will, This is a very common issue for the t connectors if it is not grounded properly. You will want to make sure that you have the ground attached securely to the clean, bare metal surface of the frame.