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T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

Item # 118650
Our Price: $68.61
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Custom Fit Vehicle Wiring

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Custom Fit Vehicle Wiring 118650 - 4 Flat - Tekonsha
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Quickly and easily install a 4-way trailer connector on your vehicle with this custom wiring harness. T-One connector plugs directly into existing wiring. Powered ModuLite reduces strain on wiring system. 1-636-306-4830 to order Tekonsha custom fit vehicle wiring part number 118650 or order online at Free expert support on all Tekonsha products. Great prices and Fastest Shipping for T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector. Custom Fit Vehicle Wiring reviews from real customers.
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  • Reviews (51)
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Tekonsha Custom Fit Vehicle Wiring - 118650

  • Custom Fit
  • Trailer Hitch Wiring
  • 4 Flat
  • Powered Converter
  • Tekonsha

Quickly and easily install a 4-way trailer connector on your vehicle with this custom wiring harness. T-One connector plugs directly into existing wiring. Powered ModuLite reduces strain on wiring system.


  • Provides a 4-way flat trailer connector at the back of your vehicle to power your trailer's signal lights
    • Compatible with 5-pole, 6-pole and 7-pole adapters (sold separately)
  • Connects quickly and easily
    • Locate connection points in rear cargo area
    • Plug in T-connector
    • Run hot lead to car battery
  • Includes ModuLite power converter to ensure that your vehicle's wiring matches that of your trailer
    • Powered module connects to battery to avoid overloading vehicle's electrical system
  • Constructed of 16-gauge bonded wire
  • Comes with dust cap for 4-way flat connector


  • Maximum amperage:
    • Stop/turn lights: 5 amps per circuit
    • Tail lights: 7.5 amps per circuit
  • 1-Year limited warranty


This custom-fit T-One connector plugs into your vehicle's wiring harness, which is located inside your rear cargo area, behind the tail lights on both the driver's side and passenger's side. You will need to remove some interior paneling to access this harness. Once you've plugged in the T-connector, run the hot lead up to your car battery. Connect the lead to the included fuse holder, and then connect the fuse holder to the positive terminal on your battery and insert the provided fuse.

Once installation is complete, the 4-way flat connector will be stowed in your rear cargo area.

It is recommended that you use a small amount of grease on all electrical connections - the plugs on your automobile and the 4-pole connector itself - to help prevent corrosion.

ModuLite Powered Tail Light Converter

A ModuLite power module is built into this T-One connector. Because most trailers run on a two-wire system - wherein the brake and turn signals are carried on one wire - the separate brake and turn signals from your vehicle's three-wire system need to be combined so they are compatible with the wiring system of your trailer. This power module functions as a tail light converter to combine the brake and turn signal functions of your automobile so that they run on one wire to properly activate your trailer's tail lights. Note: This will not affect how the tail lights on your vehicle operate.

With a ModuLite, your trailer's lights will be powered without overloading your vehicle's electrical system. Because the module draws power directly from your car's battery and bypasses the electrical routes that are used by a basic wiring harness, there is virtually no draw on your tail light circuits.

118650 Tekonsha T-1 T-Connector - 4 Wire - Modu-Lite Converter Included

Installation Details 118650 Installation instructions

This Product Fits The Following Vehicles

California residents: click here

Customer Satisfaction Score:

Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118650

Average Customer Rating:  4.7 out of 5 stars   (51 Customer Reviews)

Quickly and easily install a 4-way trailer connector on your vehicle with this custom wiring harness. T-One connector plugs directly into existing wiring. Powered ModuLite reduces strain on wiring system.


Wasn't sure what to get, customer service was excellent helping me choose. The whole kit worked great and had everything I needed. Awesome videos of how to install in my 2012 Sprinter. I always recommend e-trailer as first choice to other colleagues and friends. Thanks guys!

Mercedes-Benz Sprinter

Everything fit my sprinter van perfectly. I tend to be skeptical of things I order, but this product exceeded all expectations. Quality appears to be great, and the instructions were very clear, not at all like the instructions you often get with products these days that were obviously written by someone for whom English is clearly not their native language. I found an excellent etrailer youtube video that showed an alternate way to install the wiring which turned out to be a better option for my situation because my sprinter van is already fitted out and it would have been a problem to try to run the wires overhead and interior the way the written instructions suggested.

2013 Mercedes-Benz Sprinter

I installed it tested and it works great
The positive black wire is a couple fit short
But a previously ordered 6 ft of 16-1-1 cable
It's thinner than in the harness but it can be used, so I added
The installer on video had enough cable because it's a shorter Van.
You may not see to much on pictures because
I fished the wire to the passenger side inside around door frame
On both tail lights on pictures is no wires !
they All inside
Would recommend this to a friend

Mercedes-Benz Sprinter

Easy to install and easy directions to follow. Harness has been in my sprinter van for over a year now and works great still.

2007 Freightliner Sprinter

This product seems to be well made. Being fairly competent I installed it myself in about 6 hours and found the video on your website helpful. Regarding Video: I found that; feeding the trailer connection plug wire down under the bumper cover tricky and required loosening the cover further; The running of power cable underneath worked easiest(I opted to drill a small hole in the upper side of the battery box.) and that it might not be long enough to run up and down the inside.
Also for me removing the taillights with out braking the plastic side pins/clips difficult having not had to do it before. I would recommend watching other installation videos [online] for more tips/ideas on ways to run wires etc..


exact fit, simple installation


Solid build as I would expect from DrawTite. Installation was easy. Needed to buy additional bolts ($95) because Sprinter Factory bolts were removed by previous owner.

2008 Freightliner Sprinter

This is the place to go to for trailer needs. Everything was done professionally. From updates on order to shipping. Instructions are very clear and easy anyone could do it. Thank you!!!!!!


Was easy to install and the instructions were clear.


Haven’t done much towing but kit install went very smoothly.


First time buyer. Omg how great of a company. Everything u need and then some. Free shipping. And truth be told I had the pleasure of speaking with Terri N when I went to check out. 5 minutes into the phone call,I was thinking to myself what a wonderful person she is. Your company should feel very greatful to have someone like her working for u. I can not began to say it was the best buying experience I have had in a long time. Once again I want to say what a great place and Terri N what a wonderful person. Thank u again


Everything was great but the 12g wire going from back of van to the battery was about 6' short. No biggy but...

I recommend viewing the video that we have on a 2011 Mercedes Sprinter starting at mark 8:08 on how we ran the power wire to the battery without needing extra wire. We also have an helpful FAQ on running the power wire.
-- Etrailer Expert Jenny N - 12/03/2021

2008 Mercedes-Benz Sprinter

Bought for my 2008 Dodge Sprinter LWB van and was easy to install by following directions to the letter. Works as it should and am perfectly happy as it was a good deal price-wise as well. Bought a hitch here also and would give it the same review. Thanks.

Still working great and have had absolutely no problems. Thanks again for a product that was easy to install and does the job it was designed to do well.
Dudley P - 05/30/2021

2011 Mercedes-Benz Sprinter

The product does not work as stated. It was easy to instal, it did connect to wiring harness and there was enough wire to do the job. But the power pack that came with it doesn't have enough power to run all the lights causing the van to constantly thinks the lights are out. Also the light don't work half of the time because of this. It has been worked on many time and the problem has not be fixed.

There are a couple of possible causes for the problem youre experiencing. Some vehicles have bulb-out sensors that cause the taillights on the vehicle and trailer to hyperflash when its sensed that a bulb is out. If the trailer has LED lamps that only draw a fraction of the current of incandescents, the sensor reads the low power draw as a bulb out and the trailer lamps wont work properly. Another possibility is that the converter is overloaded as you suggested. If the trailer has more lamps than the normal stop/turn/running lamp and a few marker lamps, and the bulbs are incandescent, the draw could be exceeding the 5 amp/circuit stop and turn and 7.5 amp taillight circuit capacity of the converter. Ive linked to a help article that explains how to troubleshoot a trailer wiring harness.
-- Etrailer Expert Mike L - 07/07/2018

Mercedes-Benz Sprinter

This is on a custom kit to add trailer wiring to a Sprinter van.
The kit had everything I needed to do the job. I might have had to supply a few of my own zipties but I don't recall at this point.
Easy to install for an experienced mechanic with some electrical knowledge. Might be borderline difficult for average do-it-yourselfers. The final result was perfect.
One thing I had to cover on my own is this kit requires a power wire leading all the way to the battery. That wire a about 3 feet short. I spliced in an extension and all was good but....... In the manufacturers defense our Sprinter is a long and tall version so it would have the longest run to the battery of all these models. But still the kit is said to fit all and 3-4 feet more wire is only pennies.


Used this trailer wire loom on my 2007 Sprinter van. Very complete kit, had plenty of wire length and all the connectors fit where they were supposed to. Saved me many hours of measuring, splicing, crimping, etc. Be sure to connect the red power wire, on mine I ran a thin-wall plastic tube (drip irrigation tubing works great) as a conduit up to near where the auxiliary frame wiring come through the floor under the drivers seat and connected 12AWG wire to a 12V source.

2011 Mercedes-Benz Sprinter

Plugged right in to my 2011 170 sprinter. You just have to find a power source and the rest is plug to plug. Perfect for those of us without factory trailer wiring. It was tough to fish from drivers side to passenger side and I found it easier to cut the plug off and resplice once down the passenger side pillar.


My hitch and wiring harnesses arrived sooner than I expected in generally good shape. the hitch was chipped around the receiver which will happen anyway but you always want new stuff you buy to be perfect. I installed the hitch already and don't expect anything out of the ordinary on the wiring. I purchased wiring and the brake controller earlier on and all went well so I assume it will on my van as well.


The harness was fairly easy to work with. I took one additional step to keep the flat 4 pin outside the van. I did this by removing the black rubber rear entry threshold and drilling a hole thru the metal floor underneath. I ran the wiring through the hole and replaced the threshold and bypassed shutting the doors on wires when using a trailer.

2011 Mercedes-Benz Sprinter

The kit had everything needed. I watched the excellent installation video on line several times. This made the process stress-free.

The product arrived quickly and in good condition.

The components are of high quality. They fit exactly right, clicking into position as advertised.

The only minor quibble: the black wire that goes to the battery was about 18 inches too short. I have the longest version of a Sprinter van, so that might have been the problem. No worries. I spliced in some additional wire, problem solved.

2007 Mercedes-Benz Sprinter

This trailer wiring harness for my 2007 Dodge Sprinter works perfectly! It was super easy to install, and works completely without any issues. I'm so glad I ordered this one!

2010 Ram 2500

easy install , just watch etrailer video and they walk you through it . I installed the 4 way trailer kit on a 2010 m.b. sprinter 2500 and there was everything you needed in the kit . save yourself money and do it yourself .

2013 Mercedes-Benz Sprinter

Hitch installation was super easy. Everything fit perfect and if you follow the instructions it is almost effortless. I have not installed the T-one wiring yet as that looks more involved and I haven't had time. But the hitch is great.

2015 Chevrolet Silverado 2500

Wire supplies to connect to battery was not long enough for MD 2500 15 passenger van.

Hitch installation was easy.


It holds up pretty strong after a year. 2016 Mercedes Sprinter

Show More Reviews

See what our Experts say about this Tekonsha Custom Fit Vehicle Wiring

  • Trailer Wiring Harness Recommendation for 2012 Mercedes Benz Sprinter
    The recommended trailer wiring harness for your 2012 Mercedes Benz Sprinter is the part # 118650. This is a custom fit harness for your Sprinter that just plugs in line with the taillight harness of the vehicle and doesn't' require any hardwiring.
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  • Trailer Wiring Recommendation for 2007 Mercedes Sprinter RV Chassis
    For your 2007 Dodge Sprinter RV chassis the brake and turn signals are sent along separate wires. A converter is required unless the vehicle is equipped with a tow package plug. The tow package plug has already been converted. If you need a 4-way and you HAVE the tow package you only need the part # 118381, if you do not then you'd need the part # 118650 which does use a converter box.
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  • Trailer Hitch and Wiring for 2013 Mercedes Sprinter 2500 with Factory Step Bumper
    For your 2013 Mercedes Sprinter 2500 with a factory step bumper you'd want the Curt hitch part # 13358 which is a confirmed fit and has plenty of towing capacity. To add 4-way trailer wiring all you'd need is the part # 118650 which is easy to install and is very reliable. I also attached a help article link on picking out the correct ball mount as well.
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  • Trailer Hitch Recommendation For 2008 Dodge Sprinter 3500
    If your 2008 Dodge Sprinter 3500 has a 144 in wheelbase and a factory step bumper, then the Curt Class lll Trailer Hitch, part # 13375 is designed for your van. This hitch has a 2 inch receiver opening. This hitch has a 5,000 gross trailer weight towing capacity. This hitch is rated for up to 7,500 lbs if a weight distribution system is used.You will want to check your owner's manual or with your dealership to make sure you do not exceed the towing capacity of your van. If you plan on...
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  • Hitch and Wiring Recommendation for a 2012 Mercedes Sprinter Van
    For a hitch for your 2012 Mercedes-Benz Sprinter van with a 144 inch wheelbase and a step bumper you would want the Curt Trailer Hitch Receiver # 13358 that you referenced. For a 2012 Sprinter van with a 144 inch wheel base without a step bumper you would want a Curt Hitch # 13358. For trailer wiring you would want a Tekonsha # 118650 harness. This will work on Sprinter vans with and without step bumpers. Check out the installation videos I attached below. Now to convert the 4-way to...
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  • Trailer Hitch Recommendation for a 2011 Mercedes-Benz Sprinter 2500 144 inch Wheelbase
    For a hitch that has been confirmed as a fit for the 2011 Mercedes Sprinter 2500 with a 144 inch wheelbase you would want the Draw Tite hitch part # 75549. If you wanted to do some towing you might be interested in etrailer ball mount kit # 989900. It comes with 2 ball mounts; one with a 3/4 inch rise or 2 inch drop and one with a 2-3/4 inch rise or 4 inch drop. It also includes a 1-7/8 inch ball, 2 inch ball, hitch pin with clip, and a storage bag. If the ball mount kit does not include...
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  • Recommended Trailer Hitch Receiver For 2011 Mercedes-Benz Passenger Van W/ 144" Wheel Base
    For your 2011 Mercedes-Benz Springer Passenger Van with the 144" wheel base you will need the Draw-Tite Max-Frame Trailer Hitch Receiver - Custom Fit - Class III - 2" # 75601 if you have the factory step bumper, or the # 75549 if you have the standard bumper. If you are needing a vehicle wiring harness as well I recommend the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # 118650. I included a few videos of the products mentioned for you to take a look at.
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  • Hitch and Wiring Recommendation for a 2012 Mercedes Sprinter Van 2500 w 170 Wheelbase
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    The Bully Black Bull LED Hitch-Mounted Step # BBS-1104L should work well on your 2006 Subaru Baja as long as you have a 1-1/4 inch hitch installed. For the light to function on the # BBS-1104L you will need to have a functioning 4-way on your vehicle. If you do not have one you would need a Tekonsha # 119179KIT wiring harness. I attached installation instructions and an installation video for you to check out.
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    You can have a reverse light signal for a trailer's hydraulic coupler lockout in either the 5-pole or 7-way wiring formats. If a vehicle has a basic 4-pole harness like # 118650 that fits your 2011 Sprinter you can add another circuit for the reverse light signal simply by adding 5-pole adapter # 20036. This wires to the reverse lights to get you the signal you need. Please see the linked videos. A 7-way has a reverse light signal carried on the center contact as shown in the linked photo....
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  • Installing a Brake Controller in a 2013 Mercedes-Benz Sprinter Chassis
    For your 2013 Mercedes-Benz Sprinter, the Prodigy P3 # 90195 installation will not be identical to the 2008 Dodge Sprinter installation in the attached video you were referring to. For your installation, you will need the Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat # ETBC7 to wire the controller to your battery and to the trailer connector. I've attached a video to help further with the install on a 2013 Mercedes-Benz Sprinter to assist. This...
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  • Hitch for 2012 MB Sprinter 3500 with 170 Extended Wheelbase
    The Draw-Tite Max-Frame Trailer Hitch Receiver # 75549 fits a 2012 Mercedes-Benz Sprinter 3500 with the 170" wheelbase (and standard bumper) and as long as it does not have the 30-3/8" frame, measured outside to outside of frame. If you have the factory step bumper then you need the Draw-Tite Max-Frame Trailer Hitch Receiver # 75601 instead which has the same criteria for fitment. If you're looking to tow with the Sprinter then you need the T-One Wiring Kit # 118650 and a ball mount kit...
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    According to Curt, Trailer Hitch, # 11730, is designed to fit the hatchback and convertible models of the 1997 Saab 900. This hitch comes with the compatible ball mount, hitch pin and clip. For a ball, you can use # 19256 (1-7/8 inch diameter) or # 19258 (2 inch diameter). For trailer wiring, use Tekonsha # 118650. I have included a link to the installation details and a link to a video showing a typical installation.
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    On a 2010 Mercedes-Benz Sprinter there is not a wiring harness plug under the dash. Whether you have the Factory 7-way or not, there is not wiring connected for a brake controller. If you don't have the 7-way, then you can use the # ETBC7 wiring kit along with a 4-way trailer connector like # 118650 if you don't already have one. If you already have the factory 7-way, then you can use wiring # 5506 to connect the electric brake controller to your battery and to your 7-way trailer connector...
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  • Wiring for 2013 Mercedes Benz Sprinter to Connect to Trailer's 7-Way
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  • Recommended Hitch for a 2015 Mercedes-Benz Sprinter and Location of Tow Package Wiring Harness
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    In order to install a trailer brake controller like the excellent Tekonsha Prodigy P3 # 90195 that you referenced on your Sprinter, you will also need to install a fully functional 7-Way connector at the rear of the RV if this is not already present. If there is not a connector installed on the Sprinter chassis, then you will need to start with a 4-Way. I recommend the Tekonsha T-One Vehicle Wiring Harness # 118650. This custom harness will install by plugging into built-in ports behind...
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  • What Towing Setup Would Work For My 2012 Mercedes Sprinter
    When installing there is a few parts you would need to start the installation. For the vehicle side you would need to start with part # 118650 which would give you the beginning 4 flat plug. From the 4 flat plug you would need part # ETBC7 which would make the 4 flat into a 7 round, and also giving you the additional wiring needed to activate your trailer brakes. On the trailer side part # e99011 would provide the attachment to plug into the ETBC7. For the brake controller part # TK90160...
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Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Jeff D
Installed by:
Jeff D
Employee Jameson C
Expert Research:
Jameson C
Employee Adam R
Expert Research:
Adam R
Employee Jeffrey L
Expert Research:
Jeffrey L
Employee Joshua S
Video Edited:
Joshua S
Employee Wilson B
Updated by:
Wilson B
Employee Isabelle B
Updated by:
Isabelle B
Employee Alexander C
Written by:
Alexander C
Employee Brent H
Test Fit:
Brent H

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