Tekonsha T-One 118539 4-Way Flat Wiring Harness
Tekonsha T-One 118539 4-Way Flat Wiring Harness — Product description
Adding trailer lights to a vehicle that never had them? The Tekonsha T-One wiring harness plugs straight into your factory taillight connectors and gives you a 4-way flat output. No cutting, no splicing, no guesswork. It's the clean way to wire up running lights and turn signals for a small trailer.
The Tekonsha T-One wiring harness is the clean way to add a 4-way flat trailer connector to a vehicle that came without one. Instead of cutting into your factory wiring and hoping the splices hold up, this one plugs straight into the connectors already sitting behind your taillights. It's a direct replacement for the OEM harness on the applications it's built for.
Here's why that matters. Tapping trailer lights the old way meant scotch-locks, electrical tape, and a real chance of a corroded connection two seasons down the road. The T-One skips all of that. You unplug the factory connector, plug the T-One in between, and route the 4-way flat out to the back. No cutting. No splicing. No guessing which wire is the left turn signal.
Once it's in, you get the four standard trailer functions on a flat connector: running and tail lights, left turn and brake, right turn and brake, and a ground. That's everything a small utility trailer, a boat trailer, or a lightweight camper needs for legal, working lights on the road.
One honest note on fitment. The T-One line is vehicle-specific. Each part number is built to match the connectors on a particular set of years, makes, and models, so the plug on this harness has to line up with what's behind your taillights. Part number 118539 covers its own application list. Before you order, confirm this one matches your vehicle. If you're not sure, send us your year, make, and model and we'll check it for you.
And know what it isn't. A 4-way flat carries lighting only. If you're towing a trailer with electric brakes, you'll need more than this, a brake controller and a heavier connector. But for standard trailer lighting on a vehicle that never had a factory tow package, the T-One is about as simple as it gets.
Key Features
- Custom-fit T-One connector plugs into the vehicle's OEM taillight wiring, no cutting or splicing
- Supplies a 4-way flat output for running lights, turn signals, brake lights, and ground
- Direct replacement for the factory wiring harness on its listed vehicle applications
- Vehicle-specific design means the connectors match your factory harness for a clean install
- Handles standard trailer lighting for utility, boat, and light camper trailers
- Tekonsha engineering, the industry name in trailer wiring and brake control
Why Buy from NVN Marine
- Authorized Tekonsha reseller, full manufacturer warranty
- NMEA member and ABYC certified, advice from real boat techs
- Same-day shipping before 3 PM ET on in-stock items
- NY headquarters and Fort Lauderdale flagship retail store
Technical specifications
| Title | 4-Way Flat Replacement For OEM Wiring Harness |
|---|---|
| Brand | Tekonsha |
| Manufacturer Part Number | 118539 |
| UPC | 016118110517 |
| Series | T-One |
| Connector Output | 4-Way Flat |
| Connection Type | Custom-fit plug-in T-connector |
| Application | Vehicle-to-trailer light wiring |
| Fitment | Vehicle-specific, confirm by year, make, and model |
Frequently asked questions
Will this harness fit my vehicle?
The T-One line is vehicle-specific, so part number 118539 fits its own list of years, makes, and models. Confirm it matches yours before ordering. Send us your year, make, and model and we'll check it for you.
Do I have to cut or splice any wires?
No. That's the whole point of the T-One. You unplug your factory taillight connector, plug the T-One in between, and you're done. No scotch-locks, no tape, no cutting.
What trailer functions does a 4-way flat cover?
Four: running and tail lights, left turn and brake, right turn and brake, and a ground. That covers standard lighting on a utility trailer, boat trailer, or small camper.
Will this run electric trailer brakes?
No. A 4-way flat carries lighting only. If your trailer has electric brakes, you'll need a brake controller and a heavier connector on top of the lighting circuit.
Do I need special tools to install it?
Basic hand tools and a little patience to reach the connectors behind the taillights. Because it plugs in, there's no wiring gear or test light required.
Is this a genuine Tekonsha part?
Yes. It's the genuine Tekonsha T-One harness, part number 118539, with the full manufacturer warranty.
