Tekonsha 118855 T-One 4-Way Flat ModuLite HD Harness
Tekonsha 118855 T-One 4-Way Flat ModuLite HD Harness — Product description
The Tekonsha 118855 is a T-One tow harness built around a circuit-protected ModuLite HD converter module. It pulls power straight from your vehicle battery to run the trailer lights, so the trailer's electrical load never rides on your vehicle's light circuits. The 4-way flat plug handles running lights, brake, and turn signals for a boat or utility trailer.
If you tow a boat trailer, a utility trailer, or a small camper, the wiring is where a lot of the headaches start. The Tekonsha 118855 T-One connector assembly takes that guesswork out. It's a plug-in harness paired with a circuit-protected ModuLite HD converter module, and it gives you a clean 4-way flat connection at the back of your tow vehicle.
Here's what makes the ModuLite HD worth having. Instead of tapping the trailer lights into your vehicle's existing light circuits, the module draws power directly from the battery. Your vehicle's wiring only sends the signal, and the module does the heavy lifting. That keeps the extra load off your factory harness and away from the vehicle's electronics, which is exactly what you want on a newer truck or SUV with sensitive lighting circuits. The converter also takes separate turn and stop signals and combines them into the single stop-and-turn signal a 4-way flat trailer expects.
The circuit-protected part isn't marketing. If something shorts out on the trailer side, a bad ground, a pinched wire, a corroded bulb socket, the module's built-in protection steps in so the fault doesn't travel back into your vehicle. For anyone who's ever melted a factory harness chasing a trailer wiring gremlin, that peace of mind is the whole point.
The 4-way flat output covers running lights, left and right turn signals, and brake lights, plus a ground. That's everything a standard boat or utility trailer needs. It does not carry a circuit for electric trailer brakes or a backup lamp, so if you're towing something heavy enough to need brakes, you'll want a 7-way setup instead.
One thing to check before you order. T-One harnesses are built to plug into a specific vehicle's factory connector, so confirm this part number is listed for your year, make, and model. When it's the right fit, install is genuinely plug-and-play, with no cutting and no splicing. And when you're not sure, our crew can help you match it up.
Key Features
- Circuit-protected ModuLite HD converter module draws power directly from the vehicle battery, keeping the trailer's electrical load off your factory light circuits.
- 4-way flat output runs trailer running lights, left and right turn signals, brake lights, and a ground for a standard boat or utility trailer.
- Built-in circuit protection guards the vehicle's wiring if a short, a bad ground, or a corroded socket shows up on the trailer side.
- Converts separate stop and turn signals into the combined stop-and-turn signal a 4-way flat trailer connector expects.
- T-One plug-in design connects to the vehicle's factory wiring with no cutting and no splicing when matched to the correct application.
- Heavy-duty (HD) module handles the extra current of larger or LED-heavy trailer lighting without straining the vehicle.
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 | T-One Connector Assembly With Circuit Protected ModuLite HD Module, 4-Way Flat |
|---|---|
| Brand | Tekonsha |
| Manufacturer Part Number | 118855 |
| UPC | 016118163100 |
| Connector Type | 4-Way Flat |
| Converter Module | ModuLite HD (Heavy Duty) |
| Circuit Protection | Circuit protected |
| Harness Style | T-One plug-in connector assembly |
| Application | Trailer tow wiring harness |
Frequently asked questions
What does the ModuLite HD module actually do?
It's a powered converter that pulls current straight from your vehicle battery to run the trailer lights. Your vehicle's wiring only carries the signal, so the trailer's electrical load stays off your factory light circuits. It also combines separate stop and turn signals into the single stop-and-turn signal a 4-way flat trailer uses.
What does a 4-way flat connector power?
Running lights, left and right turn signals, brake lights, and a ground. That covers a standard boat or utility trailer. It does not include a circuit for electric trailer brakes or a backup lamp.
Will this run electric trailer brakes?
No. A 4-way flat connection has no brake circuit. If your trailer is heavy enough to need electric brakes, you'll want a 7-way setup and a brake controller instead.
What does circuit protected mean on this harness?
The module has built-in protection so a fault on the trailer side, like a short, a bad ground, or a corroded bulb socket, doesn't travel back and damage your vehicle's wiring.
Do I have to cut or splice any wires to install it?
When it's matched to the correct vehicle, the T-One harness plugs into your factory connector, so there's no cutting and no splicing. Confirm this part number is listed for your year, make, and model before you order.
Does this work with LED trailer lights?
Yes. Because the heavy-duty module powers the lights directly from the battery rather than through the vehicle's circuits, it handles both incandescent and LED trailer lighting.
