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  1. Custom Fit Vehicle Wiring
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  4. Trailer Hitch Wiring
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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 # 118786
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Custom Fit Vehicle Wiring

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Tekonsha Custom Fit Vehicle Wiring - 118786
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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. 1-800-940-8924 to order Tekonsha custom fit vehicle wiring part number 118786 or order online at etrailer.com. Free expert support on all Tekonsha products. Guaranteed Lowest Price 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 (153)
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Tekonsha Custom Fit Vehicle Wiring - 118786

  • 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.


Features:

  • 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 behind tail lights
    • Plug in T-connector
    • Run hot lead to car battery
  • Includes ModuLite power module that connects directly to battery to avoid overloading vehicle's electrical system
  • Constructed of 16-gauge bonded wire
  • Comes with dust cap for 4-way flat connector


Specs:

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


Installation

This custom-fit T-One connector plugs into your vehicle's wiring harness, which is located behind the driver's-side and passenger's-side tail lights. You will have to remove the access cover and the tail light assemblies to access this harness.


T-One Connection Location Points Behind Tail Lights

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 beneath your vehicle. A mounting bracket (sold separately) is recommended to keep the connector secure.


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 Power Module

A ModuLite power module is built into this T-One connector. 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.



118786 Tow Ready T-1 T-Connector - 4 Wire - Modu-Lite

Replaces Tekonsha 118782

Installation Details 118786 Installation instructions

This Product Fits The Following Vehicles



California residents: click here



Customer Reviews

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector - 118786

Average Customer Rating:  4.9 out of 5 stars   (153 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.

by:

Quality product.
Followed the provided
video and aside from routing the power wire through the frame being a bit fiddly, the install was a snap.
If you have a few common tools and a little mechanical ability, install is a breeze.


Comments
No complaints. Item is worth every penny. Install video was exc.
Tim - 05/04/2022

by:

I contacted etrailer in advance of buying the items needed to add a trailer hitch to my 2021 Wrangler unlimited Sahara. I was assured everything would bolt right up and the wiring kit was made specifically for my new jeep. When I received my wiring kit, it was for a jeep with the battery on the opposite side of the vehicle. So the instructions were different and it was more of a chore routing the wires from the battery to the tail lights. Just barely had enough wire to reach the other side of the vehicle. I ended up having to hire a shop to facilitate the install and spent over $200 for the install due to the difference between the items, instructions, and my Jeep. I wouldn’t be so frustrated except I took the time to reach out to etrailer staff and I was assured there would no problems.


Comments
When it comes to routing the power wire to the battery you can route the wire over to the passenger side at the rear of the front, it does not matter and it will not have any affect on the install or the system. You will just want avoid places where the wire would be pinched or exposed to heat along the frame rail. We do have a FAQ that is helpful.
-- Etrailer Expert Jenny N - 03/21/2022

by:
2019 Jeep Wrangler

Very satisfied with the etrailer wiring harness for my 2019 Jeep Wrangler JLU. Installation instructions were good. Components and wiring are of good quality and sufficient length. Would buy again!



by:
2018 Jeep Wrangler

I installed this on my 2018 Wrangler and it was perfect. Very simple install. Videos were very helpful. Took about 3 hours by myself. It may have taken a little longer because I ran the battery wire inside the frame for protection. Seems to be very good quality and I would recommend this harness to anyone needing to add a trailer light plug to their vehicle. Thanks etrailer.



by:
Jeep Wrangler

Installed on 2021 Jeep Wrangler Unlimited with Curt Trailer Hitch Receiver - Custom Fit - Class III - 2" Item #C13392. It's been a year since I installed it, but I believe it did not require a dedicated power line, which makes the install easier.



by:
2018 Jeep JL Wrangler Unlimited

I prefer to use this Tekonsha module for the vehicle that don`t have the factory tow harness. The module was tucked away in the body cavity behind the drivers side tail lamp assy. All wiring was covered in HD split loom. All wiring was concealed as much as possible by running them through the cross rail and frame rail up to the battery positive terminal. I did lengthen the green wire on the passenger side to accomplish this. All connections were done with heat shrink connectors. Installation did take longer than usual based on the wire routing I chose. Overall I am totally satisfied with this product.



by:
Jeep Wrangler

Nice straight-forward installation videos helped to be sure I was getting everything right. Quality product that has worked great for over a year and counting. 2021 Jeep Wrangler Unlimited.



by:

Easy to match the hitch I needed with my vehicle using the website. I was also able to pick out the wiring harness I needed as well. After being ordered it was shipped quickly with an email providing shipping and tracking information. Perfect fit to my vehicle. Very pleased with my purchase.



by:
2020 Jeep Wrangler

Kit worked great, had some trouble getting passenger side wiring pulled up in taillight housing due to small opening to access. I had to remove a lower splash guard panel in wheel well to get better access. I pulled power wire to battery thru passenger side frame, worked out great with electrical snake.



by:

Nice easy install. Wish it had heat shrink for the connectors, or heat shrink connectors.


Comments
Still Working great!
Kynndarrn - 04/29/2022

by:
2018 Jeep Wrangler

I've purchased a handful of trailer hitches/wiring harnesses over the past 10 years and they have always been awesome!! Quality products and fast shipping every time!! Just recieved a new class 111 hitch & wiring harness for my 2018 Wrangler JL and installed the hitch in less then 10 minutes and the wiring was approximately an hour after watching the video provided on their website. Never been disappointed!!



by:
Jeep

This product was very easy to install connected perfectly to the factory connectors took some time to route the wires safely. Was the only kit I found for 2021 Jeep JL



by:

Easy to install, great product. ETrailer never fails me.


Comments
Very easy to install. No issues to date. Very happy with product.
Michael - 03/29/2022

by:
2019 Jeep Wrangler

When I order from e-tailer I know I'm getting a quality product, and the right product. The wiring harness fit great. The thing I really love about e-tailer is the video's they have showing you just how to install the products.



by:
2022 Jeep Wrangler

As advertised, installation is not overly difficult. Simply watch the video, figure out your own way, then plug and play! Plenty of wire and length, had zero issue on the install, took less than an hour!



by:

Straight forward and etrailer always has the resources to make installing simple and straight forward.



by:

very easy install thanks to the outstanding video. Adding this and an $80 -2 inch receiver was way cheaper than buying from the dealer. Since I had the taillights off, i threw in a fuel filler door at the same time.



by:

This harness worked as it should!


Comments
Although I do not own this vehicle any longer, when I put this harness to use it worked flawlessly. I have since purchased another harness for my Subaru wilderness and it was a breeze to install and also works as advertised. Im a fan of etrailer!
Fiverwheel - 12/28/2021

by:

this makes wiring ease they!! should make it for all of the towed vehicles!!



by:

Nice installation kit. Absolutely everything you need but the tools.



by:

Fast delivery, have not installed wiring harness yet but it looks very high quality and easy to install



by:
2020 Jeep Wrangler

I Received the kit very quickly and in good condition. Installation was easy and the kit came with everything needed to complete the install. The wiring, connectors and installation accessories were all high quality pieces.
I did add convoluted loom to all of the wiring that is exposed to the elements for good measure.



by:
2018 Jeep Wrangler

My Jeep is a 2018 Wrangler Unlimited JL Sport S with the standard halogen headlights and not the LED upgrade. I wired this T-One kit up in about 4 hours. I have pretty good mechanical knowledge and I'd say this kit is something that would be intimidating for someone who's never done it before. I ended up using a large part of the tools in my garage including a drill, various bits, a stick magnet (dropped the ground screw down into a cavity on the Jeep and couldn't find it), 1/4" ratchet, long extension, various sockets, flashlight, pliers, trim tool, wire crimp tool, lighter, T40 torx socket, extra zip ties, flat blade screw driver, etc. I used the grommet on the firewall behind the brake booster to run the power wire from the battery into the cabin of the Jeep. Tucked the power wire under the door sill trimwork all the way to the rear. Had to disassemble a large part of the trimwork at the rear of the Jeep to access the grommet that goes down into the driver side tail light. Then I was able to do my connections inside the cavity for the tail light, mount the converter box in there, and route the 4-pin and passenger side T-connector out the back of the cavity near the fuel filler tube. From there, across the top of the crossmember, and up into the passenger side tail light from the bottom. To do the install properly, it took a while and a good assortment of tools and a little knowledge of how plastic trim panels are attached so that you can remove them without breaking them. If you're not comfortable disassembling your new Jeep, order the factory tow package!! But if you want to save $650, order the hitch and wiring here at this site and do it yourself on a Saturday. Installation was a pain, but the kit included everything I needed (except the assortment of tools) and was well made. Trailer lights all work as expected. Hopefully the wiring will give me years of service.


Comments
Still works great a year later. Did need to apply dielectric grease to the pins on the trailer connector but all seems well.
Shawn - 04/29/2019


by:

Good quality. Fits and works as design ed.



by:

Have purchased two of these and have had no problems with either. Good sound products.


25
153
Show More Reviews

Ask the Experts about this Tekonsha Custom Fit Vehicle Wiring



  • Trailer Wiring Harness Recommendation for 2018 Jeep Wrangler JL
    The trailer wiring harness I recommend for your 2018 Jeep JL Wrangler 4-cylinder is the Tekonsha kit part # 118786 that you referenced. This is a custom fit harness which means it will install easily and it comes with a very reliable converter box so it will last a long time too. I attached an install video for this kit on a 2018 JL just like yours for you to check out as well.
    view full answer...
  • Trailer Wiring Harness Recommendation for 2018 Jeep Wrangler JL
    For your 2018 Jeep Wrangler Unlimited Sport with LED taillights the Tekonsha kit part # 118786 that you referenced is a confirmed fit and will work great. This kit has the highest amperage rating which means it will be the most resilient to wiring shorts and overdraws, and installs very easily so it's overall the best choice. I attached an install video for this on a similar 2018 Jeep Wrangler JL as yours for you to check out as well.
    view full answer...
  • Trailer Wiring For 2018 Jeep JL Wrangler
    The Roadmaster Universal HyPower diode wiring kit part # RM-154 is different wiring than what you need for towing a trailer with the 2018 Jeep Wrangler JL. You will need a 4-pole flat wiring harness part # 118786 which will plug in behind the Jeep's tail lights. You will plug the trailer connector on the trailer into the 4-pole to power the lights. I have attached an installation video for your reference.
    view full answer...
  • Best Trailer Wiring Harness for a 2018 Jeep JL Wrangler Sahara
    Yes, the T-One Vehicle Wiring Harness part # 118786 which replaced the T-One Vehicle Wiring Harness part 118782 is now compatible with Sahara and Rubicon editions of the 2018 Jeep JL Wrangler.
    view full answer...
  • Does Trailer Wiring for 2018 Jeep Wrangler JL Unlimited Have to Run to Battery Post
    Not all vehicles can handle the additional amperage draw of the trailer taillights on the vehicle taillight circuits. Those vehicles need setup that draws power from the battery. Some vehicles have higher rated circuits that can handle this, and others need to have the power drawn straight from the battery to protect the taillight circuits. For your 2018 Jeep Wrangler Unlimited JL you need to install a harness that draws power from the battery to protect the taillight circuits. For that...
    view full answer...
  • Best Trailer Wiring Harness for a 2018 Jeep JL Wrangler Rubicon
    Yes, the T-One Vehicle Wiring Harness part # 118786 will work on all 2018 Jeep JL Wranglers with factory LED and incandescent lights. This is actually an updated harness that was made to replace the T-One Vehicle Wiring Harness part 118782 that had issues with certain packages. There will be no issues whatsoever using the T-One Vehicle Wiring Harness part # 118786 on your 2018 Jeep JL Wrangler Rubicon.
    view full answer...
  • Can Trailer Wiring be Run Under 2018 Jeep Wrangler JL
    You can absolutely run the 12 volt hot lead of the T-One Wiring Harness # 118786 under your 2018 Jeep Wrangler so long as you can find a way to route it to your battery. In fact, the linked directions state this as an option, which you can see by the accompanying cut out.
    view full answer...
    Image 1 for
  • No Power to 7-Way on a 2018 Jeep Wrangler JL
    Which pin are you testing on your 2018 Jeep Wrangler JL's 7-way? If it is the 12 volt power feed then you will need to check for a blown fuse. In the power distribution center (PDC) on your Jeep there will be a pink 30 amp fuse in the F37 slot that controls 12 volt power to the 7-way. If you are referring to the brake, stop/turn, or tail light pins then these will only show power while the circuit is active.
    view full answer...
  • How to Install a Trailer Wiring Harness on a 2019 Jeep Wrangler
    Yes, the installation of a trailer wiring harness will be different for a 2019 Jeep Wrangler MOAB when compared to a 2013 Jeep Wrangler MOAB but not by much. Instead of just plugging in one connector behind the driver side tail light you will need to plug in a connector behind the passenger side tail light as well, run a power wire to the Jeep's battery, and ground the harness to a bare metal surface. For the above, I recommend using the T-One Vehicle Wiring Harness with 4-Pole Flat Trailer...
    view full answer...
  • Trailer Wiring Recommendation for 2019 Jeep Wrangler JL
    We have a confirmed fit for custom trailer wiring for your 2019 Jeep Wrangler JL as part # 118786 that we know will fit and work well. We can't really tell you if our competitors are up on the most current fit info though.
    view full answer...
  • Troubleshooting No Running Lights After Installing Tekonsha Harness on 2018 Jeep JL Wrangler
    There are a couple possible reasons as to why the running lights are not working after installing the Tekonsha T-One Vehicle Wiring Harness # 118786 on your 2018 Jeep Wrangler JL Unlimited. First, since this harness does require that a hot lead be run up to the vehicle's battery, I recommend making sure all the connections under the hood are secure. Since the Jeep's battery is what will actually be powering the harness, you will want to ensure that the black power wire from the T-Connector...
    view full answer...
  • 2018 Jeep Wrangler JL Unlimited 4-Way Trailer Wiring Harness
    For your 2018 Jeep JL Wrangler Unlimited the correct trailer wiring harness is the Tekonsha part # 118786 which is a confirmed fit. This installs by plugging inline with the taillight wiring of your Jeep to operate the trailer wiring. Of the trailer wiring brands on the market the Tekonsha brand is the most reliable.
    view full answer...
  • Custom Fit Trailer Wiring Harness Recommendation for 2018 Jeep JL Wrangler
    For the 2018 Jeep Wrangler JL that you have we have the Tekonsha 4-way kit part # 118786 which is a confirmed custom fit and would work well. This installs by plugging inline with the tailight harnesses of your Jeep as you can see in the install instructions I attached below.
    view full answer...
  • No Power to 7-Way On A 2018 Jeep Wrangler
    Then it is possible that your 2018 Jeep Wrangler is not equipped with a trailer tow package. I did take a look at the owner's manual for the Jeep and F37 is the correct fuse placement if the Jeep is equipped according to the manual. Did you just install the 7-Way plug? If so, you may need to have the towing functions activated at the dealership. This is a fairly common issue.
    view full answer...
  • Estimated Installation Time for Tekonsha 118786 Trailer Wiring Harness on 2019 Jeep Wrangler
    Tekonsha doesn't list an estimated installation time for their trailer wiring harnesses like they do with their trailer hitches, but after looking through the install instructions and viewing the linked installation video, I'd estimate that the install should take a professional about an hour, and a fairly capable do-it-yourselfer about an hour and a half. I'll also link to a help article that addresses how to run the wire from the rear of the vehicle up to the battery.
    view full answer...
  • Wiring Harness for a 2022 Jeep Wrangler
    Yes, there is a wiring harness that does not require cutting or splicing wires available for your 2022 Jeep Wrangler. It is the Tekonsha T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector item # 118786. This custom-fit T-One connector plugs into your Jeep's wiring harness behind your rear tail lights. It plugs in-line without having to cut into the harness.
    view full answer...
  • Troubleshooting Trailer Wiring of Jeep Where Only 12 Volt Accessory Circuit Works
    Typically this problem is caused by corrosion or dirt on the trailer wiring pins. I'd first try cleaning all of the pins of the 7-way with sandpaper and make sure none of them are bent or damaged. Other place to check is fuses under the hood of the vehicle if the wiring is OEM. You can also check to make sure the wiring behind the connector isn't damaged. I attached a link to a page that covers trailer wiring troubleshooting for you to check out as well.
    view full answer...
  • Recommended 4-Way Trailer Wiring Harness for 2019 Jeep Wrangler Unlimited
    The correct Tekonsha 4-Way harness for your 2019 Jeep Wrangler Unlimited is the T-One # 118786. This will plug right into factory ports behind the driver and passenger side tail lights. The included powered converter then needs to be ran up to the Jeep's battery to safeguard the vehicle's wiring and ensure enough power gets back to the trailer lights. This will provide you with just the needed 4-Way connector to activate the trailer's basic signal lights (without brake or 12V power functions)....
    view full answer...
  • 4-Way Trailer Wiring Harness Recommendation for 2018 Jeep Wrangler Unlimited
    For trailer wiring the most reliable brand we offer is the Tekonsha brand by far so it's the brand I recommend the highest. So for that you'd want the # 118786 which is a confirmed fit for your 2018 Jeep JL Wrangler Unlimited and is compatible with the taillight style you have.
    view full answer...
  • Trailer Wiring Harness for a 2018 Jeep JL Wrangler Unlimited Sahara
    Apparently the 2018 Jeep JL Wrangler Unlimited Sahara and Rubicon models have a different type of tail light and the connectors on old wiring harness 118782 do not match up. In order to add a trailer connector on those models or other JL models you will need to use # 118786.
    view full answer...
  • 2018 Jeep Wrangler Unlimited Rubicon Trailer Wiring Harness Recommendation
    For your 2018 Jeep Wrangler Unlimited JL Rubicon the T-One 4-way harness part # 118786 is a confirmed fit that will not cause any dash lights to come on. This would be a great solution. This is our most reliable trailer wiring brand so we recommend it the highest. It installs by plugging inline with your taillight assemblies which allows it to function without the vehicle wiring even knowing it's there.
    view full answer...
  • Does Trailer Wiring Harness have to Connect to Battery on a 2018 Jeep JL Wrangler
    There are several reasons why the power wire has to connect directly to the vehicle battery when installing trailer wiring harness # 118786 on your 2018 Jeep JL Wrangler. First, the 12 volt accessory circuit was not designed to support the additional power draw of the trailer wiring harness. A wiring harness must have its own dedicated fused connection to the battery. Second, attaching the power wire to the battery maintains the level of separation between the vehicle wiring and the...
    view full answer...
  • Is Splicing Required to Install Trailer Wiring Harness 118786 on 2018 Jeep JL Wrangler Unlimited
    No, installation of trailer wiring harness # 118786 does not require splicing into the vehicle tail light wiring. It has connectors that plug in line with the tail light connectors on the 2018 Jeep Wrangler Unlimited JL models. A connection to the battery is required and will be what powers the trailer lights as well as part of what helps protect the Jeep's electrical system.
    view full answer...
    Image 1 for
  • Will Trailer Wiring Harness 118786 Work on a 2018 Jeep JL Wrangler Unlimited with LED Tail Lights
    I checked with Tekonsha, the manufacturer of wiring harness # 118786, and there are no known issues with this wiring harness and LED lights on the new 2018 Jeep JL Wrangler Unlimited.
    view full answer...


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Info for this part was:

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