Tekonsha 118405 4-Way Flat OEM Replacement Harness
Tekonsha 118405 4-Way Flat OEM Replacement Harness — Product description
The Tekonsha 118405 is a 4-way flat replacement harness that restores your factory tow wiring without any cutting or splicing. It plugs into your vehicle's OEM connector and gives you a clean, standard 4-flat output for trailer lights. Simple to install, built to Tekonsha's towing standards.
If your factory tow package wiring has taken a beating, or you just need a clean 4-flat connection at the back of the vehicle, the Tekonsha 118405 is a straight replacement. It's a T-connector style harness, which means it plugs into your vehicle's existing wiring rather than forcing you to tap, cut, or splice into anything. That's the whole point. You get factory-style wiring without the guesswork.
The 4-way flat is the workhorse connector of the towing world. Four pins, four functions: taillights, left turn, right turn, and a ground, with the brake signal riding along the turn circuits. That covers just about every small trailer out there, boat trailers, utility trailers, small campers, and cargo haulers that run basic lighting. If your trailer plug is the flat four-pin style, this is the connector that mates to it.
Installation is about as simple as trailer wiring gets. Because it's a plug-in replacement for the OEM harness, you're not chasing wires or reading a color chart. You unplug the old or damaged harness, plug this one in, and route the 4-flat to the back. Most folks can have it done in a driveway with basic hand tools. No soldering iron, no praying you tapped the right circuit.
Tekonsha has been building towing electronics for a long time, and it's a name a lot of us trust when it comes to brake controls, breakaway systems, and wiring. This harness carries that same reputation. It's the kind of part you want on a boat trailer that lives half its life backing down a wet ramp, or a utility trailer that sees hard use. Reliable trailer lighting isn't optional. It's the difference between a legal, safe tow and a ticket, or worse.
One thing to be clear about: a 4-way flat handles lighting only. It doesn't carry a circuit for electric trailer brakes or a reverse light. If your trailer needs those, you're looking at a different connector and possibly a brake control. But for standard trailer lighting on a 4-pin flat setup, this replacement harness does exactly what it should, and it does it without drama.
Key Features
- 4-way flat connector: mates to any standard flat four-pin trailer plug for taillights, brake, and turn signals
- T-connector design: plugs directly into the vehicle's OEM wiring with no cutting or splicing
- Direct OEM replacement: swaps in for a damaged or worn factory tow harness
- Tekonsha build quality: from an industry leader in towing electronics and trailer wiring
- 4-pin flat output: fits boat trailers, utility trailers, cargo trailers, and small campers running basic lighting
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 | Tekonsha |
| Manufacturer Part Number | 118405 |
| UPC | 016118058581 |
| Connector Type | 4-Way Flat |
| Harness Style | T-Connector |
| Application | Replacement for OEM tow package wiring harness |
Frequently asked questions
Does this harness require cutting or splicing?
No. It's a T-connector style replacement, so it plugs into your vehicle's existing OEM wiring. You unplug the old harness and plug this one in.
What does a 4-way flat connector control?
The four pins handle taillights, left turn, right turn, and ground, with brake lights combined into the turn signal circuits. It covers standard trailer lighting.
Will this work with electric trailer brakes?
No. A 4-way flat handles lighting only. If your trailer has electric brakes, you'll need a different connector and a brake control.
What kind of trailers use a 4-flat connector?
Boat trailers, utility trailers, cargo trailers, and small campers that run basic lighting are the common ones. If your trailer plug is the flat four-pin style, this mates to it.
What tools do I need to install it?
For most vehicles, basic hand tools are enough. Because it's a plug-in replacement, there's no soldering or wire stripping involved.
Is this a genuine Tekonsha part?
Yes. It's Tekonsha part number 118405, and we're an authorized Tekonsha reseller with full manufacturer warranty.
