To see if this custom-fit item will work for you please tell us what vehicle you'll use it with.
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Hooking up trailer lights doesn’t have to mean cutting into your truck’s wiring. The Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector plugs straight into the factory tail light connectors. Everything fits the way it should, no splicing or tracing wires required. Once installed, you’ve got a clean 4-flat connector ready for your trailer’s running lights, turn signals, and brake lights.
Bad grounds are one of the most common reasons trailer lights flicker or fail. This harness includes a white ground wire designed to attach directly to clean, bare metal on the frame. That solid connection keeps voltage consistent across all circuits so your turn and brake lights work every time. It’s a simple but critical fix for many of the electrical gremlins that show up when towing.
Some vehicles send out separate signals for stop and turn lights, which can confuse trailers that use a single wire for both. The Curt harness includes an integrated converter that combines those signals properly so your trailer lights work like they should. If you ever test it with a circuit tester, you’ll see full power on each of the four functions when everything is wired right.
If you plan to add a brake controller or upgrade to a 7-way setup later on, this harness gives you the foundation you need. Pair it with a 4-to-7-way adapter kit and you can easily add electric brakes or 12V power without redoing your wiring. It’s a plug-and-play starting point that makes future towing upgrades simple.

Customer Satisfaction Score:
98% were satisfied with this product
2% of customers were not satisfied
Ratings & Reviews

Alex H.
5/7/2015
No problems so far with a years use. Again can not stress how simple the install was. Hard to go wrong with their products.

Marc
6/15/2021
Product works great, no issues

Joe A.
4/15/2015
Have finally installed the product and it work exactly as advertised! Quite easy to install, also.

John T.
2/16/2020
Like a champ I really love your products
Do you have a question about this Custom Fit Vehicle Wiring?
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Mike L.
6/21/2019
For the parking lights, the first step would be to find if the problem is in the vehicle wiring or in the trailer wiring itself. Use a circuit tester on the pin of the trailer connector fed by the brown wire while the vehicles headlights are on. If the pin shows power, the wiring harness and converter is fine. If it does not show power, and the connections are fully seated in place, then the wiring harness is faulty and should be replaced. The issue with both turn signals firing at the same time is a classic manifestation of a ground problem. Make sure the trailers main ground connection on the trailer tongue is securely fastened and not loose or corroded. Make sure each trailer lamp is securely grounded to the trailer frame, and that each connection is not corroded. Ive linked you to a help article about troubleshooting trailer wiring, I hope youll find it helpful.
Helpful Links
faq-4-5-way-troubleshooting.aspx