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Vehicle to Vehicle Tail Light Converter

Vehicle to Vehicle Tail Light Converter

Item # 118158
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Tow Ready Tow Bar Wiring - 118158
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Used when a motorhome with a 2-wire system is towing another vehicle with a 3-wire system, by way of a tow bar. Lowest Prices for the best tow bar wiring from Tow Ready. Vehicle to Vehicle Tail Light Converter part number 118158 can be ordered online at or call 1-833-496-1390 for expert service.
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Tow Ready Tow Bar Wiring - 118158

  • Tail Light Converter
  • Splices into Vehicle Wiring
  • Universal
  • Tow Ready

Used when a motorhome with a 2-wire system is towing another vehicle with a 3-wire system, by way of a tow bar.


  • Used when a motorhome is towing another vehicle by way of a tow bar
    • If the towing vehicle has a 2-wire system and the vehicle being towed is on a 3-wire system (the vehicle has amber turn signals, separate from the brake signals), the vehicle to vehicle tail light converter will need to be used
  • This item cannot be installed backwards (the input going to the output side) to convert a tow vehicle down
  • Will not work with vehicles that have LED tail lights
  • Limited 1-year warranty

Note: You will need to install a tail light isolating diode system (38955) and 2 additional diodes (RM-792) with this tail light converter to prevent electrical feedback when flat towing a vehicle. Vehicles with separate turn signals and brake lights will need a total of 6 diodes.

118158 Vehicle to Vehicle Taillight Converter

Replaces 31820

Installation Details 118158 Installation instructions

California residents: click here

Customer Reviews

Vehicle to Vehicle Tail Light Converter - 118158

Average Customer Rating:  4.8 out of 5 stars   (130 Customer Reviews)

Used when a motorhome with a 2-wire system is towing another vehicle with a 3-wire system, by way of a tow bar.


This product works well with some thought and acknowledgement that it has limitations.

I have just bought my second one. The previous one failed after five years.

This new one etrailer recommend the use of diodes to prevent feedback to the towing vehicle.
This is not a bad idea but was not previously available.

The circuit diagram that comes with this unit was misleading to me.
Eventually I figured it out and will passon what I learned.
My trailer has separate orange indicators.
It is wired as all my trailers are with a seven way plug.

You will see each diode having three connections.
Two from the towing vehicle and one to the indicator bulbs.
I just used one of the diode input tags connected to the appropriate wire from the seven way.
The output I fed to the indicator bulbs.
I have three indicators on each side of the trailer and they can all run off of the same tab.

I am enclosing a few pictures.
The first one is the old unit which was housed in a separate box screwed to the chassis.
Then I had a second box which held all the connections.

The second picture shows the new unit contained in its own box with the five diodes used.
The box is just a plastic project box from Radio Shack.

The last picture is of the finished unit all sealed and ready to go.

Now for those limitations.
Do not expect this to work as though it were an extension of a four wire vehicle.
The indicators will work and the brake lights work BUT the indicators go off when the brake is applied.
The unit cannot run the separate indicator and the brake at the same time.

No problems so far
Peter - 10/11/2021


I gave up trying to find a wire to tap for a third brake light on a 2013 GMC Sierra, so I ordered a 2 to 3 wire adapter ( #118158) as recommended by you expert Michael H. He stated that only one of the inputs was needed, but both Left and Right turn were required to make mine work at all. That aside, the product was received quickly and installation was simple using the enclosed diagrams. I have never seen anything mentioned anywhere about waterproofing undervehicle connections. I do and they last for years.

Does the 3rd brake light flash when using the hazard lights?
-- comment by: Sam - 05/06/2015
Yes, emergency flashers will flash the third light also.
-- comment by: - 05/24/2015


This converter worked great for what I intended it for. I was wanting to add a third brake light to back of my fifth wheel trailer. I purchased STL179RB Glolight Thinline LED also. I tried to wire this direct. It won't work, it flashes when you turn the turn signal on. A friend of mine recommended this after doing a search on the etrailer website. Etrailer support recommendation was installing two lights. Duh! that's why I wanted a third brake light, I already have two lights that function as stop/tail/turn. The installation in these pictures is not complete. I was trying to avoid drilling holes in the back of my trailer, I still may have to. I am going to enclose the wires going up the trailer to the light in some white wire loom. The light at present is secured with only white RTV, not sure that will hold. I'm still trying to avoid drilling new holes, may have to though. I hooked up all the wires on the input side, white to ground, green to right stop/turn, yellow to left stop/turn. I hooked only the red wire to red wire of the light on the output side. I hooked the ground (white wire) of light to input side of converter. Yes, it works and no it does not blink when either blinker is turned on. The additional two wires on the output side of converter are not being used nor is the additional wire of the light. Sorry for the long review, don't usually write reviews at all. Anyway, if this will help even one person it will be worth it.


I use Optronics oval LED lighting exclusively and I don't think this was made to work with them because of the rapid response of the LEDs. I use this so that on a 4 wire system I can have turn signals on the side of the trailer. When you first hit the brakes, there is a fast blip of light from the side marker/turn signals. With an incandescent bulb it would be too fast to light the bulb. This is something I can live with. I think this works great with no problems so far.


First off the customer service at etrailer is by far the best that I have dealt with. If I had a question, they sent me an email response very quickly. Secondly, the shipping is extremely fast. I placed the order and it came to an APO AE address (military stationed in Germany) via USPS Priority Mail and it arrived in like 5-7 days, I was shocked when it arrived, because I was expecting at least another 3 or 4 days.

So, as far as the product. Works great and was just what was needed.
Project was to make an adapter that I could plug into my 2017 Jeep Grand Cherokee U.S. spec and use a German trailer. My friend did all of the wiring and made the adapter, so I do not take any credit for any of it. Just sharing this, to those trying to figure out if it can be done.
Moving on, the adapter is a 7 pin/blade normal American plug that goes into the back of the JGC and the other end of the adapter is the 13 pin German (European) socket. We tried it without this product and all worked except when you hit the brakes the brake lights were faded and the blinker lights were lit up as if they were the brake lights. So, had to get this product and separate the brake/blinker light on the American side and have separate brake and turn wires on the German side.
Put this product between the two in the middle of the adapter, wired it up and all works great!
I used 2 zip ties around the product and a bunch of electrical tape to hold it to the adapter, at least to give it a better look.

Now I only have to plug in the adapter whenever I use a German trailer and all works correct. When done towing, remove the adapter and everything is back to the American system. Did not have to cut/splice or do anything to the wires on the JGC or the trailer, all was done at the adapter.

Thanks again to etrailer for providing awesome customer support and shipping!


The "Vehicle To Vehicle Tail Light Converter", Item #118158 is serving my needs well. I refitted my trailer completely using all LED lights. I mounted the converter inside the "C" channel underneath my tongue mounted toolbox for a little added protection. I also soldered all connections throughout the re-wire and used heat shrink &/or liquid rubber over all connections. I feel that proper planning prevents poor performance. I ordered numerous lights from etrailer also, and all are working fine. When I chose to call them with a question about one of their products, it was answered quickly and appropriately. I am a business person, and that's customer service!

The tail light converter is still working fine. I have no regrets.
Jim R - 04/06/2021


I was looking for a way to add a third tail light to a vintage trailer and this proved to be just the ticket. Easy to install and worked great right out of the box.

Plenty of communications from etrailer staff along the way. Just wish they would provide tracking info so you could plan for expected receipt date.


Since my trailer is 100% LEDs, I would not have chosen this for the two to three wire conversion since the description specifically states "not for LEDs". But after a discussion with the tech guys, I installed it and it has worked flawlessly.


Used to add little LED marker turn lights on the corners to vintage two circuit airstream trailer. The led corner lights now are red running at night, red stopping by day and switch to yellow, when turning, day or night.


Interested in adding a third light up higher on your trailer for additional visibility? This product will separate the turn signal and brake signal on a four pin connector so you can add a running and brake light up higher to be visible. Simulates the third light that most cars and trucks have these days in the center of the back window. Positive for the semi-trucks visibility. You do not really think they can see the normal trailer lights 12" off the ground when following close behind or coming over a hill do you?
Included a picture with just the running lights illuminated.
Thank you etrailer for having the right products in stock! Most other dealers did not know what I was talking about and one even told me it was against the law. Called state highway patrol and they encouraged the additional third light! I also added the higher side running lights when semi's are merging behind you at night.


Shipping was fast. Installation was easy. Works as designed. Couldnt ask for a better result. Now my tow car is all wired correctly.


I am always able to find exactly what i need here at I put a camper shell on my tow vehicle and I had to wire up the high center brake light. I called Sal to find out if there was a device to kill the blinker signal to the light, and he knew exactly what i needed. It was an easy and pleasant experience. I highly recommend Sal, he is very knowledgeable and easy to work with. Thank you for the great service!


This is the second time I have purchased tow brackets and wiring kits from etrailer. Wouldn't buy from anyone else. They know their stuff.


Great service on a part I wasn't aware was available. Was going to use a 7 pin adapter to power seperate lights on a little camp trailer. This will simplify my needs.


Perfect for connecting the tail lights from my RV to my car on the car dolly.


This product was used to separate the brake light signal from the turn light signal on a Ford F-350 cab/chassis with a flatbed to facilitate using amber turn signals without them illuminating when the brakes are applied (truck only, no trailer). So far they are "functioning as designed" and I'm very happy with the product.

Still working fine.
Gregory V - 10/09/2019


I installed a European 13pin receiver on a 2018 Ford Explorer and stowed the wiring adapter under the vehicle. Worked flawlessly so far with caravans and bike carriers.

Still working flawlessly, even with lots of snow, ice and sludge
Christian G - 03/01/2021


Works great hooked it up on my Ford truck to split up the turn signals and the brake lights on my trailer


Fairly easy to install, and worked as e xpected.

No problems, so much better than a tow dolly of past years. Used it on several trips without problems.
Ronald - 02/25/2022


I have used etrailer many times and have always been satisfied. If you need parts for campers, towing, etc., this is the place to go.


Still working great!
Install was easy,
their online help and install videos make installation a breeze.


Easy painless installation!
I used
this product to install a third brake light on my TC Teardrop camper.


Easy install process, reviewed and illustrated in easy to follow wiring diagrams provided in the kit. etrailer on YouTube for the install of this tail light converter was complete and professionally illiustrated


I purchased this tail light converter over a year ago. This eliminated the problem of electrically connecting a European trailer to my U.S. spec Dodge Dakota truck. It was easy to install and works perfectly. I also appreciate etrailer waiting a year before asking me to review this product as most on line vendors ask for a review before the item is received.


My taillight adapter arrived quickly, undamaged, and exactly as advertised. Prior to ordering, I emailed techs with a question. They responded quickly and with excellent advice.

This little converter is simple to install. My trailer has a shared turn signal/brake wire. The adapter allows me to connect a lighted license plate frame that also has a third brake.

What great customer service! You guys and your products are fantastic. The items I bought are working 100
John D - 03/05/2015

Show More Reviews

See what our Experts say about this Tow Ready Tow Bar Wiring

  • Can the Tow Ready Vehicle to Vehicle Taillight Converter be Used on a Boat Trailer and Get Wet
    The Tow Ready Vehicle to Vehicle Taillight Converter, # 118158, is typically used on motor homes that are towing another vehicle by way of tow bar. The converter is not a sealed box so if it were to be submerged in water or exposed to rain, it would be damaged. If you choose to use this part on your boat trailer, you will want to make sure that the converter is mounted in a location that protects it from water.
    view full answer...
  • Are Diodes Required to Separate Brake Lights from Turn Signals Using Converter 118158 on Trailer
    That is exactly what converter # 118158 was designed for. You will not have to use diodes, although you could if you wanted and it wouldn't hurt anything, because there is only one input circuit for each of the wires. The red output wire would go to the brake light wire on each tail light. Yellow would go to left turn signal and green would go to right turn signal.
    view full answer...
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  • Wiring A Trailer So That Turn Signal And Brake Signal Are Separated
    You will want to find lights that match the lights you currently have on your trailer. If you have incandescent lights I recommend either staying with incandescent or swapping out all of the lights to LEDs. LED lights draw much less power, so you may want to go that route. I have attached a helpful article that explains how the trailer wiring is run. In order to separate the brake signal from the you will need part # 118158. This will take the signal from the vehicle that has the turn...
    view full answer...
    Image 1 for
  • Installing Side Mount Turn Light on Trailer with Combined Brake,Turn Signals
    To wire a trailer in the way you describe you will need to use a vehicle-to-vehicle taillight converter, part # 118158. The converter will be wired inline on the trailer wiring and will break out the turn and brake circuits. I attached a drawing that shows how I would go about wiring this converter on a simple 4 wire trailer. You would need to cap off the red wire on the output side of the converter and tie that wire up out of the way, since you will not need to run it to the back of the...
    view full answer...
    Image 1 for
  • Can LED Lights on Boat Trailer Guide Posts be Wired as Running Lights, Turn Signal and Brake Lights
    The lights on the guide posts on your boat trailer have only one input wire and one ground wire. You would be able to have them be powered by the running light circuit or the turn signal/brake light circuit but not all 3. Usually the guide post lights are wired into the running light circuit so they can be seen all the time at night.
    view full answer...
  • Taillight Converter for European Trailer
    The Tow Ready Vehicle to Vehicle converter, part # 118158 will indeed split the brake light circuit back out from the right and left turn circuit, so it will indeed do what you're wanting it to do. We do not ship to Europe, so if you have a friend or relative in the US, you could have them order the item for you and then have it shipped to you in Europe. Another alternative would be to use a freight forwarding service, which you can find online.
    view full answer...
  • How to Wire 3-Function Reverse/Turn/Stop Light in Vehicle with Combined Stop/Turn Wiring
    In order to install your 3-function lights on your 1997 Dodge Ram 3500 that has combined stop/turn wiring you will need a vehicle-to-vehicle taillight converter, part # 118158 from Tow Ready. This converter separates the combined stop/turn functions into separate signals that run on separate wires. This converter will work only on incandescent lights, but not with LEDs. Your vehicle running/tail light wire will bypass the converter and go directly to the wire on your lights that operates...
    view full answer...
  • Dimension of the Vehicle to Vehicle Taillight Converter # 118158
    I spoke to my contact at Tow Ready about the dimensions of the Tow Ready Adapter part # 118158 and he told me that the top of the box is 2.9 inches by 2.8 inches. He couldn't get the thickness of the box though, and since we don't have one in stock right now I wasn't able to get that dimension for you.
    view full answer...
  • Trailer Wiring for 2007 Jeep Wrangler Towing Utility Trailer with LED Lights
    All of the 4-pole flat trailer wiring harnesses we offer for your 2007 Jeep Wrangler (shown on the link at right) do not have built-in converters; they pull the power for the trailer's lights directly from the Jeep's taillight wiring. On a 4-pole vehicle connector the stop and turn signals are already combined; the yellow wire carries left turn and stop signals and the green wire carries right turn and stop signals. The brown wire carries running light signals for both sides of the trailer. It...
    view full answer...
  • Will Vehicle to Vehicle Tail Light Converter # 118158 Work to Power a 3rd LED Brake Light
    You can use the vehicle to vehicle tail light converter # 118158 to power a third brake light whether it be LED or incandescent. The input green wire will connect to the combined right turn/brake light circuit and the yellow wire will connect to the combined left turn/brake light circuit. White gets grounded to the vehicle or trailer frame. On the output side if you just need the brake circuit it is the red wire. The green and yellow output wires can be capped off and stowed out of the way.
    view full answer...
  • Vehicle to Vehicle # 18158 Taillight Converter for Separate Turn Signals on 2003 Jeep Wrangler
    For what you are trying to accomplish, you shouldn't need the diodes. The # 118158 vehicle to vehicle taillight converter you referenced would convert the 3 wire system you have now to the 4 wire system you want. Diodes are for use when one vehicle is towing another, and you don't want the signal from the towed vehicle feeding back into the electrical system of the tow vehicle. I'd recommend installing the converter in an interior location if at all possible. The converter isn't designed...
    view full answer...
  • Wiring Side Marker Lights on Trailer as Turn Signals
    Using a relay would be the way to go if you wish to use those fog lamps as reverse lights. You would want one input on the relay tapped into the reverse light circuit, and one leg ran to a 12-volt power source. There would be no really simple method of getting a side marker light to serve as a directional signal without having it light when the brakes are applied. How to make your connections will depend on the taillight system of your tow vehicle. If your vehicle has amber colored turn...
    view full answer...
  • Wiring Side Markers On Trailer as Turn Signal Using Vehicle to Vehicle Converter, Part # 118158
    You could use the vehicle to vehicle tail light converter, part # 118158. You would tap the input side of the converter into the right and left turn circuits on the trailer, and run the right and left output wires to the side markers you are wanting to use as turn signals. The brake wire on the output side would not be used, just cut it short and tape off the end so it does not short out on anything.
    view full answer...
  • Using Two Wire to Three Wire Converter Part # 118158 to Provide Third Brake Light for Trailer
    Using the Tow Ready Tail Light Converter, part 118158 should do the trick for you. If you are wanting to leave the existing tail lights on your trailer operating as both directional and brake lights, you would tap the green and the yellow wires of the converter into the appropriate wires leading to the tail lights. The red wire exiting the converter would then be used to power your third brake light. The yellow and green wires exiting the converter would not be needed, simply cut them...
    view full answer...
    Image 1 for
  • Where Do Extra Diodes Go When Wiring A Tow And Towed Vehicle With Separate Brake And Turn Signals
    The other two diodes are needed so you can have separate turn and brake signals. So you will have a diode for each brake light (right and left), a diode for each turn signal (right and left) and a diode for each tail light (right and left). I will send you a link to the wiring diagram of the # RM-154 wiring kit to show where all of the diodes are connected and what color wires go to what function on the tow vehicle. A separate wire for the brake circuit will have to be run on the towed...
    view full answer...
  • Tail Light Converter for Towing a Trailer w Separate Tail Light Wiring with a Vehicle with Combined
    You will want to use a Taillight Converter # 118158. You would wire up this unit into the wiring of your trailer. The input side of this will be run from the trailer 4-way, and the output side will go to the wiring on the trailer. Check out the video I attached that details the installation of this product. The terminology used in this video will be different because its talking about using this product for flat-towing a vehicle with another vehicle. However, if you wire it up the way...
    view full answer...
  • Converter Box Recommendation for Converting Combined Signal to Trailer with Separate Lights
    Yes, the Vehicle to Vehicle Taillight Converter # 118158 would work well to separate the combined turn signal circuits from your 2012 Subaru Outback with combined wiring to the separate wiring of your trailer. This would be the only product you would need. Basically, you would want to mount this product somewhere near the connector on your trailer and then splice the wiring in. The box is labeled to let you know exactly which wire goes where, but you will need to run the right turn/stop...
    view full answer...
  • When Hazards are Applied what Lights Will Flash on Trailer Taillights with the # 118158 Installed
    The Taillight Converter part # 118158 that you referenced is just fine. The internal circuits of the converter will flash the stop lights when the hazards are applied. This is normal.
    view full answer...
  • Can a Taillight Converter Work with a 2005 Chevy Corvette C6
    The taillight converter # 118158 you referenced will separate the blinker from the brake light on your Chevy Corvette C6. You won't lose any amperage. However, converter # 118158 will not work with vehicles that have LED taillights. I am thinking your Corvette will have LED taillights. The converter is really designed to be used when a motorhome is towing another vehicle by way of a tow bar. I added a video review for you as well.
    view full answer...
  • Does Vehicle to Vehicle Taillight Converter Require Diode System to Tow Trailer with Jeep Wrangler
    You are correct that you will not need a diode kit in conjunction with the Tow Ready Vehicle to Vehicle Taillight Converter, # 118158 in order to tow a trailer with your 2010 Jeep Wrangler. You would only need the diode kit if you were flat towing your Jeep from an RV or motorhome.
    view full answer...
  • Can the Taillight Converter part # 118158 Be Used with LED Taillights
    The LED restriction for the # 118158 is for if the converter was being used on a vehicle with LED lights. Basically, it will work if the trailer has LED taillights, but not if the tow vehicle has them. The input side of the box can't use signals from a vehicle with LED taillights, but the output side can. If only the trailer side of the wiring uses LEDs this would work just fine.
    view full answer...
  • Taillight Converter to Separate Combined Taillight Circuits
    The taillight signal converter part # 118158 that you referenced would be the correct product you would need to convert a combined taillight circuit to a separate circuit. The turn signals would only be illuminated when the blinkers are applied on the tow vehicle. They would not stay on all the time. Check out the review video I attached as well.
    view full answer...
  • Brake Lights are Dim With Turn Signal Flashing Using Converter 118158 On a Trailer
    The LED light warning is in reference to flat towing a vehicle that has LED lights. So basically for your situation the trailer (vehicle) LED lights could be the issue. An easy way to determine if it works better with incandescent bulbs would be to replace an LED brake light with an incandescent light of some kind and see if the problem persists. If it does persist then the issue could be related to the fact that converter # 118158 is not rated very high. This is just the nature of this...
    view full answer...
  • Can Trailer Wiring Circuit Converter Box 118158 be Used with Running Light Circuit
    Yes the converter # 118158 could be used with a third brake light that also has the running light circuit ran to it. The running light circuit of your wiring would bypass the converter box though. You'd use the box for getting to just the third brake light but then you'd run the running light circuit directly to the light.
    view full answer...

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