Trailer Lights, Connectors, and Wiring

Trailer Lights

Optronics submersible, under 80" trailer light kit with 25' wiring harness.

Wiring for Your Trailer

Hopkins 7-Way molded trailer wire connector.

TRAILER END CONNECTORS

Wiring for Your Vehicle

Curt T-Connector vehicle wiring harness with 4-pole flat trailer connector.

CUSTOM-FIT VEHICLE WIRING

Pollak trailer wiring mounting bracket and installation hardware.

MOUNTING BRACKETS

CURT Echo under-dash bluetooth brake controller w/ OneControl app.

TRAILER BRAKE CONTROLLER

4 WAY TO 7 WAY CONVERSION FOR BRAKE CONTROLLER

Pollak 7 pole to 4 way connector adapter.

WIRING REDUCER

Hopkins adapter 4-pole to 7-pole and 4-pole.

WIRING ADAPTERS

Articles & Guides

"How to Wire a 7 Way Trailer Plug" article.

"How to Wire Trailer Lights with a 4 Way Plug" article.

"A Trailer Maintenance Checklist" guide.

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Trailer Lights and Wiring

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etrailer.com Has Everything You Need, From Lights to Wiring and Tools

You could say we’re your one-stop shop. Keeping your trailer lights working properly isn’t just a good way to keep your trailer looking amazing; in most places, it’s also the law. Choose for our collection of tail lights, clearance lights, license plate lights, reflectors, and interior lights. We also have custom-fit vehicle wiring to make sure your trailer lights are working in tandem with your vehicle lights. We have trailer connectors and adapters, wire, wire connectors, mounting brackets, circuit breakers and testers, junction boxes and wiring tools.

With over 75 years of assisting our neighbors and customers, over 1 million photos and videos taken to make sure you’re getting exactly what you need, and over 35 thousand installations completed, we’ve got the product know-how and experience to help you make the right choices for the job at hand.

What types of trailer lights do I need?

You’ll need tail lights, clearance lights, and possibly license plate lights or reflectors, depending on your trailer and local regulations. These lights make sure you’re visible and legal while on the road. For more information on lighting requirements, visit our FAQ.

How do I figure out the right wiring harness for my trailer?

It depends on what your trailer needs and the type of connector on your vehicle. There are 4-way, 5-way, 6-way, and 7-way harnesses. A 4-way covers basic lights like turn signals and brake lights, while a 7-way adds extra features like reverse lights or electric brakes.

How do I install a 4-way trailer wiring harness?

First, find a clean metal spot on your trailer frame and attach the ground wire securely with a self-tapping screw—this is super important for everything to work. Next, lay the wires along the frame, making sure they’re out of the way of any sharp edges or moving parts, and secure them with zip ties.

Now, connect the harness wires to the trailer light wires. These control the brake lights, turn signals, and tail lights. Use wire connectors to join them, and protect those connections with electrical tape or heat shrink tubing to keep out moisture.

Once everything’s connected, plug the harness into your vehicle and test the lights. Make sure the brake, turn signals, and tail lights all work properly. If they do, just go back and secure the wires neatly along the frame, and you’re good to go! Need extra help? Check out our trailer wiring diagrams for a visual guide to get everything set up correctly.

Can I have my trailer wiring or lights professionally installed?

Yes—and sometimes it’s the smartest move. Installing trailer lighting and wiring might seem simple, but it can get tricky when you’re dealing with multiple light types, adapters, or converting from a 4-way to a 7-way setup. If you'd prefer to have a pro handle the wiring, splicing, or testing, use our Local Installer Locator Tool to find a qualified technician near you. It's a great way to make sure your lights are road-ready—and legal—without the guesswork.

My trailer lights aren’t working. What should I check?

First, make sure all the ground connections are tight and clean—poor grounding is a common issue. Then check for damaged wires, test the lights with a circuit tester, and try replacing the bulbs. It’s usually one of those!

Can I switch from a 4-way to a 7-way connector?

Definitely! You’ll need an adapter kit, like the ETBC7. It lets you add functions like electric brakes and reverse lights. Just plug it into your 4-way and wire in the extra features.

What is a junction box and how do I use one?

A junction box is a small, enclosed hub that organizes and protects trailer wiring connections. It’s where all the wires—like those for lights, brakes, and power—meet and connect to the wiring harness.

To use one, mount the box on your trailer frame in an accessible but protected spot. Feed the trailer and harness wires into the box through the openings, then connect the corresponding wires to the labeled terminals or connection points inside (e.g., brake, turn signals, tail lights). Secure the wires with screws or connectors, cover them with the terminal caps or grommets provided, and close the box tightly to keep everything safe from moisture and damage. It’s a handy tool that makes wiring more organized and easier to troubleshoot later!