T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
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1999 Pontiac Sunfire
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1999 Pontiac Sunfire
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When it comes to wiring your vehicle for towing, the hassle of splicing wires and complicated installations can be daunting. The T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector by Tekonsha makes the process as simple as it gets. This harness connects directly into your vehicle's existing wiring using custom connectors, eliminating the need for cutting or splicing. It's designed specifically for your vehicle, ensuring a snug fit and reliable performance every time you tow.
Worried about overloading your vehicle's electrical system with your trailer lights? The ModuLite power module built into this harness is your answer. By drawing power directly from the battery, it reduces the strain on your vehicle's tail light circuits. This not only protects your car’s electrical system but also ensures your trailer’s lights receive the consistent power they need, without impacting your vehicle’s tail light function.
Navigate the roads with confidence knowing that your trailer's signal lights are powered and ready to go. This harness provides a durable 4-way flat trailer connector that works seamlessly with 5-pole, 6-pole, and 7-pole adapters (sold separately). Whether you're making a quick trip or a long journey, this connector ensures your trailer's lights are in sync with your vehicle's signals for safety and reliability.
Durability is key when it comes to trailer wiring, and this harness is built to withstand tough conditions. Featuring 16-gauge bonded wire, it guarantees enhanced strength and longevity. Furthermore, the included dust cap protects the 4-way flat connector from dirt and moisture, safeguarding your connections against the elements during all your travels.
Preventing corrosion and maintaining clean electrical connections is critical for ensuring the longevity of your harness. By applying a small amount of grease to all electrical connections - including the plugs on your vehicle and the 4-pole connector - this feature helps maintain optimal performance and prevent wear and tear. This simple maintenance step can greatly enhance the durability of your wiring setup.
This will not affect how the tail lights on your vehicle operate.
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Worked fantastic. Installed on a 2015 Golf TDI drove it from the East Coast to Alaska and back. Worked flawlessly.
Works as advertised, snaps right into existing wiring. Removing interior panels of vehicle to expose existing wiring maybe the only challenge depending on your vehicle. VW e-Golf installation was pretty straight forward.
The Tekonsha was an easy install on a 2013 Passat. The hardest part of the install is removing interior trim to hide power wire. Works as designed.
I installed this harness on my 2017 Golf GTI. All tee connections fit the OEM sockets perfectly. The location I chose to mount the module required me to extend the left socket wiring (yellow wire). No big deal. There is a rubber body plug on the floorpan on the drivers side rear corner that can be used to exit the 12 volt battery wire from the rear compartment. I ran the battery wire externally underneath the chassis attaching to the brake lines using zip ties. I removed the underbody splash shield on the drivers side to access the brake lines and then reinstalled afterwards. Removing and installing the rear trim panels to gain access to run the module wires from left to right took the most time. I am very detailed oriented and I spent what time was necessary to end up with a superb installation.
The 118646 kit worked great! I called in because I was confused regarding the application listed on the box (Golf) and my car which is a Passat. The young lady on the phone was extremely helpful. When I got the confirmation, there were two videos that showed me EXACTLY how to install it. The video was clear and professional. Although I didn't enjoy crawling under the car, I was able to successfully install the kit and it even works. Thanks for your extra help.
Patrick 
6/19/2022
Works great! No issues.
It fits and works fine on my 2016 GTI SE. ETrailer is doing their customers a disservice telling them the Tekonsha wiring harness does not fit the MK7 GTI. I had read that several people had used it without issue, and went as far as contacting Tekonsha and speaking to a tech person there. They agreed that circuitry and electronics-wise, there is no difference between this and the other that would require splicing, and it comes down to whether the plugs are correct and are reading the signals on the correct wires. The plugs are an exact fit and it maps the yellow and green signal wires to the correct wires on the car harness, the same ones identified on the recommended splice harness. It would be helpful if ETrailer and Tekonsha could work together to get the application specs for 118646 updated to include the GTI so it could save customers like me time researching this, and the anxiety about buying and using something that supposedly doesn't fit.
Great product. Super happy with it. No issues. Also, when I called you guys for help, you were very helpful and friendly. Can’t recommend you enough!
Made the mechanic watch the video on installation before we got started. Hitch and wiring went on effortless..
Denny F.
8/25/2021
Works great,have a small 5x8 trailer for getting our racing kart to the track.
Oregon to Colorado in 22 hrs non stop without a single hiccup. Everything worked great
Hitch and wiring are working flawlessly. Best decision I made adding a hitch to my car to carry items that would not fit inside.
Cliff B.
3/26/2018
Everything is still working very well and I am very pleased with my purchase.
I had purchased the stealth hitch, coil over air bags and wiring harness, all products were top shelf top name and top quality, absolutely no regrets. Customer support and service were real professional and very knowledgeable. I’m still using etrailer for more products, now some of my friends are too.
Original wiring harness had a problem and did not power running lights when installed per instructions. etrailer customer service was great to work with and got a replacement product out to me promptly. All my lights are now working. Installation video clearly show how to install product and is a great time saver.
When i needed to add a trailer hitch to my car for a move, i searched around and this was pretty much the cheapest priced hitch i could find( about a hundred cheaper than uhaul) so i got it and installed myself without taking the bumper off and im very pleased with my purchase. If i ever need to put a hitch on another car i will be coming here first, thanks!!
I installed this wiring kit with the help of one other person on my 2013 VW Passat. Connecting everything in the trunk area was extremely simple due to the T-connections. Running the power supply line to the battery took the most time to ensure proper routing, but it was fairly simple. Removing protective plastic shields exposed many lines to zip tie the wire onto and ultimately made the install safe for the long term.
Wiring harness and trailer hitch for my VW Golf fit fine, no monkeying around. It took an afternoon to work through the process of installing the parts, but there were no significant snags in getting it done. Reviewing the instructions and available videos before hand were helpful.
Amazing product customer care was on point I spoke with Chelsea and she was amazing. Got everything figured out and everything here quicker than expected. Highly recommend.
I had no problems installing the trailer hitch it was like a breath of fresh air.wiring it up was very easy and I must say the connectors was an easy way to connect to the existing wiring.
RECEIVED YHE WIRING HARNESS IN PERFECT CONDITION. THE INSTALL WAS FLAWLESS. TOTAL TIME OF INSTALL WAS APPROXIMATELY 35 MINUTES AND I DIDN'T RUSH MYSELF. RUNNING THE POWER LINE FROM THE MODULE TO THE BATTERY WAS A BREEZE, THE HARDEST PART WAS JACKING UP THE ONE SIDE OF THE CAR TO ROUTE THE WINE. PRODUCT WORKS PERFECT AND EVERYTHIG FIT PERFECT. YOU CAN'T GO WRONG BUYING ETRAILER PARTS.
Wiring was fairly easy to install. Directions were easy, this was better than cutting and splicing into factory harness. The passat has a plastic skid plate that comes off and makes for easy wire runs. overall im happy with the hitch and the wiring
I want to thank my etrailer customer service contact, Ashley E for helping me finish my wiring project.
When I began preparing to install wiring harness when I realized I had ordered the incorrect part number.
I called etrailer Customer service and Ashley promptly reviewed my order and identified the appropriate harness for my vehicle. She generated an order for the correct product and arranged for the return of my incorrect product.
I was surprised and delighted to find that the new product arrived 3 days later.
The correct harness is a custom product that is connected with coupling connector that plugs in between the tail light wires and the light. All I had to do is route the power wire to the battery. It works perfectly!
Thanks Ashley and etrailer for a great experience.
Jamie S
My VW Golf tSI had a non-standard-factory rear harness in it. etrailer went out of their way to provide me with a harness that I could use in place of the one for a "normal" Golf tSI. They also spent some time with me on the phone, to make sure the replacement would work. After a year, it all still works fine!
Wiring a car to tow is nothing like the old days. I ordered the custom harness, arrived very soon, installed per the instructions and video, now my trailer is all nice and legal. I don’t have a truck, economy and long commute prohibit that, when I need one, I hook the trailer instead, E-Trailer has always had my towing solutions.
I bought this to go with the hitch I purchased for a VW Passat. This fit perfectly and has been very durable. I would recommend it for anyone looking for this size hitch.
Install isn’t that bad. Be super careful with the body panel screws on the underside of the car. IIRC the video says to lightly turn them, but the plastic gets brittle with time and they break very easily
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Gary R.
7/9/2018
After one year everything is working perfectly!