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  1. Tow Bar Wiring
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Roadmaster Diode 7-Wire to 4-Wire Flexo-Coil Wiring Kit

Roadmaster Diode 7-Wire to 4-Wire Flexo-Coil Wiring Kit

Item # RM-15247
Our Price: $145.81
Tow Bar Wiring

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Shipping Weight: 4 lbs
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Diode kit allows you to use your vehicle's tail lights and wiring system while preventing feedback from your RV. Wires 2-wire and 3-wire systems to operate as a combined lighting systems. Includes 7-wire to 4-wire Flexo-Coil electrical cord. Great Prices for the best tow bar wiring from Roadmaster. Roadmaster Diode 7-Wire to 4-Wire Flexo-Coil Wiring Kit part number RM-15247 can be ordered online at or call 1-800-940-8924 for expert service.
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Roadmaster Tow Bar Wiring - RM-15247

  • Diode Kit
  • Splices into Vehicle Wiring
  • Tail Light Mount
  • Universal
  • Roadmaster

Diode kit allows you to use your vehicle's tail lights and wiring system while preventing feedback from your RV. Wires 2-wire and 3-wire systems to operate as a combined lighting systems. Includes 7-wire to 4-wire Flexo-Coil electrical cord.


  • Lets you wire your vehicle to accept your RV's tail, brake, and turn signal lights for flat towing
  • Wires towed car as combined system so that brake and turn signals travel along same wire
  • Prevents electrical feedback and the damage it can cause to your vehicle's electrical components
  • Diodes powder coated aluminum case is corrosion resistant and provides protection from the elements
  • Brake light relay (RM-88400 - sold separately) may be required if used with supplemental braking system
  • Flexo-Coil cord is resitant to water, oil, chemicals, and has silicone-injected plugs to prevent corrosion
  • Includes: 4 Hy-Power diodes; 30' long, 4-wire harness; wire connectors; cable ties; 1 ring terminal; 3' long plastic loom, 8 ft coiled cord, vehicle mounting bracket, and socket
  • Made in the USA
  • Limited Lifetime Warranty


  • Diode Max amperage: 85 amps
  • Diode Max voltage: 24 volts
  • Coiled cord max length: 8'
  • Coiled cord retracted length: 15"

Note: For applications that have separate lighting, this kit will cause your brake lights to function as both brake and turn signal lights. A wiring converter (118158 - sold separately) and 2 additional diodes (RM-792) will be needed if you want to retain separate turn and brake signals.

Separate vs. Combined Lighting Systems

Some automobiles operate on a 3-wire system, wherein the brake signal and the turn signals travel along different wires to illuminate different lights. (Typically, these vehicles have amber turn signals.) This is referred to as a "separate lighting system". When you hook up for flat towing using this kit, your towed car's lighting system will operate in a combined fashion regardless of whether it typically has combined or separate lighting. This means that the brake and turn signals sent by your RV to your towed car will be carried on a single wire. As a result, your car's brake lights will do the flashing for the turn signals. Your vehicle will still function as designed when not hooked up to your RV.

Diode Wiring Diagram

Diode Wiring Diagram

Diode Wiring Diagram

Diode Wiring Diagram

Do You Need a Brake Light Relay?

Because this kit wires your vehicle as a combined system, a brake light relay (RM-88400 - sold separately) may be required if you use a supplemental braking system with your towing setup. A supplemental braking system depresses the brake pedal in your towed car every time you apply the brakes in your RV. So, if your towed car's brake lights illuminate when the brake pedal is pressed and the engine is off - as is the case when towing - then you need to install a relay to ensure that the lights on your towed car always act in accordance with the signals sent by your RV via the wiring harness. Without a relay, the brake signal from your towed car will override the turn signal sent by your RV when you slow down to make turns, creating a potential hazard.

15247 Road Master Towed Car 4 Diodes RV Plug to 4-Wire Socket Flexo Coil Wiring Kit

Installation Details RM-15247 Installation instructions

This Product Fits The Following Vehicles

Customer Satisfaction Score:

Customer Reviews

Roadmaster Diode 7-Wire to 4-Wire Flexo-Coil Wiring Kit - RM-15247

Average Customer Rating:  4.7 out of 5 stars   (126 Customer Reviews)

Diode kit allows you to use your vehicle's tail lights and wiring system while preventing feedback from your RV. Wires 2-wire and 3-wire systems to operate as a combined lighting systems. Includes 7-wire to 4-wire Flexo-Coil electrical cord.


This place is the best! Placed my order- easy peasy-delivered on time-
Watched install video- again made it so easy and saved $1000 installation fee!!! Thanks for being a great company and special thanks to Carol C my order specialist !!!


I installed this myself along with a tow bar from another company at the same time, in about 4 hours. installation was straightforward and worked perfectly. saved about $800 in total labor.

Gregory V.


Perfect no issues, I am very happy with the harness, I would buy this again if I change vehicles.

Etrailer Expert

Mike L.


@GregoryV We're glad to hear that, thanks!!


They work as the should.


Excellent quality and engineering. Installation requires a fair amount of mechanical sense and ability.


Not happy with the wiring kit. It didn’t work for my application. It was a good thing that I’m good with electrical because I had to make my own for my application.


Easy install, just mount it, run the wire to the break operator, plug it in and you’re good to go!


No oroblem

2017 Ford F-250 Super Duty

The 7wire to 4 wire had a short in it I ended up just using an old one I had.


It would have been 5 stars but the battery charge kit would not work with the 7 wire to 4 wire flexo coil kit, so I had to put together my own 7 wire to 6 wire harness to make things work.

Etrailer Expert

Jenny N.


I am glad that you were able to make it work. Since the 7 to 4 way Flexo coil kit comes with the 4 round plug it does not have enough connectors to attach the charge line kit to it. As you mentioned, you would need a 7 to 6 connector to allow it to work. You could go with part # RM-152-98146-7 which is a straight line kit or part # RM-152-1676-7 which is a hybrid straight line and coil kit. Since you already have part # RM-15247 then you can simply replace the 4 round connector to a six round connector with part # RM-910030-7 or part # RM-910030-5.


Very easy to install and love that it doesn't interfere with our vehicle's lighting system. Was even easier to do the installation since etrailer has a step-by-step video for our vehicle year and model.


Rapid delivery. Works as expected.


Little pricey for what you get. Needed to buy additional wiring to complete. The wiring that comes in the kit is no long enough to run from the tail lights to the connector at the front of the truck. Didn't use the flex coil wiring kit as I have a roadmaster nighthawk.

Etrailer Expert

Jenny N.


The bonded four wire that comes with the kit is 30 feet long. The installation manual advises to run the wire along the frame rail under the vehicle being careful to route it away from heat sources. You can see an install on a 2016 Ford 150 truck in the link below. I know it is not the same as your truck however the installation will be similar.

by: 08/11/2022

The instructions were accurate and the installation went well.


Great service

Ford Ranger

Perfect Fit. I watched the video's that etrailer provides and decided to take on the install myself. Everything from the base plates, diode wiring kit, drop receiver and Blue Ox Tow bar went just as the video's showed.
We are very happy with the service and parts has provided us for our 2022 Ford Ranger.

2015 Ford C-Max

I used this kit on a 2015 Ford C-Max Energi. All in all the installation kit was complete except it was missing the self tapping screw. This was not a problem since I was able to attach the ground wire to an existing ground connection without having to use the screw. It also did not have any screws (2) to attach the socket bracket to the baseplate (I used a Blue Ox BX2639 baseplate). Luckily I had a couple laying around. The hardest part was routing the wire harness throughout the undercarriage of the vehicle. I used almost all the wire ties for this part of the installation. I also had to purchase additional wire to run across the rear of the vehicle ( I needed additional green wire for the right side brake and directional and brown to jump to the other side for the parking lights. The directions provided in the kit were helpful but I relied quite a bit on the installation videos you provided. I found the videos provided much more detail and guidance.

1995 Jeep YJ

I installed this on my 1995 Jeep YJ. After watching the video a couple of times, to get an idea of what I was getting myself into, this job was fairly simple. It took me about 4 hours total time, and when I plugged the wiring harness into my truck and all the brake & taillights worked perfectly on the Jeep.

2014 Jeep Grand Cherokee

As you can see, I ordered the components necessary to allow me to flat tow my Jeep Grand Cherokee behind my motorhome. I followed the recommendations made by one of your employees as far which components would be necessary to meet my objective. Now that I have utilized this equipment to tow our vehicle over two separate trips to Seattle, Washington and also to Tucson, Arizona, I can report that we have been very satisfied with every aspect of our purchase. Thank you, again, for the expert assistance!

2009 GMC Sierra

etrailer has been fantastic to work traffic after the sale was timely and informative as to when my items would ship, when they would arrive and then follow up if I was satisfied...this wiring kit assembly was easy to install...I utilized the provided directions and videos provided on this site and others...happy with the service, happy with the product, will order again

2005 Jeep TJ

Never flat towed before, enlisted etrailers help on what to get. Just returned from a 4000 mi trip to the northwest ! Had no problems towing a 2005 Jeep lj behind my motor home. Thank you etrailer for your assistance and great videos! Installed the system myself! Very happy!


Removed the wiring after the main computer module on the car failed shortly after installing it. Coincidence? Maybe. But I wasn’t going to take any chances.

Etrailer Expert

Katrina B.


I have gotten in touch with the manufacturer and they have said that the complication could be from not installing the diodes correctly. Did you use a brake light switch kit? If not, then the Roadmaster Diode 7-wire to 4-wire Flexo-coil Wiring kit will not work properly. If you do not have a brake light switch, then we recommend using a custom fit brake light switch # RM-751455.


One major draw back that is see is that none of the wire connector spades you crimp on the end of the wires were of the Heat Shrink type. This leaves the wire exposed to water and possible corrosion. Need to spend the extra $$$'s and upgrade the spade connectors to the Heat Shrink type.

2012 Jeep Liberty

This looks like a good quality lighting kit and was easy to install on my 2012 Jeep Liberty.

Christopher D.


Still working great!

2018 Jeep JL Wrangler Unlimited

Easy install. This is my second wiring kit I have installed and with both, I only wish that an additional four or five feet of wire was supplied. Both times, I had to butt connect a couple of wires to get across from one tail light to the other.


Easy peasy install, good directions

Show More Reviews

See what our Experts say about this Roadmaster Tow Bar Wiring

  • Can Roadmaster Tow Bar Wiring RM-15247 Be Used On 2015 Jeep Wrangler Unlimited
    Since the wiring kit has a different use than the Ready Brake system on your Wrangler Unlimited, they can both be used at the same time. The Roadmaster Tow Bar Wiring, part # RM-15247 lets you use the Jeep tail lights and wiring system and will operate with the RV brake, turn, and tail light system. With the included diodes, it helps prevent electrical feedback which can cause damage to the vehicle wiring.
    view full answer...
  • Testing Flat Towing Diode Kit on 2006 Mini Cooper
    In a flat towing diode wiring setup such as with Roadmaster Diode 7-Wire to 4-Wire Flexo-Coil Wiring Kit # RM-15247 you can test the functionality of the installation on the toad by applying 12V power from a spare battery or even from the Mini's battery. You'll want to confirm which pin on the vehicle connector is grounded, either to the battery negative terminal or to a chassis ground. This should be the wire with the ring terminal. Then one at a time apply +12V power to the other pins...
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    Image 1 for
  • Tow Bar Wiring Recommendation for 2018 Jeep Wrangler JL Unlimited
    The Roadmaster Diode kit part # RM-15247 is a confirmed fit for your 2018 Jeep Wrangler JL Unlimited. It also comes with an umibilical adapter to span the tow bar that has a 7-way connector on it. This kit wires into the taillight circuits of your vehicle and allows the tow vehicle to operate the taillights of the vehicle.
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  • What Is Best Flat Towing Wiring Harness for 2020 Ford Escape
    We don't have any tow bar wiring kits for your 2020 Ford Escape that are plug and play but the diode kit part # RM-15247 that you referenced would be the easiest and best option. This does come with install instructions and I also attached an install video you can use as a guide that shows the kit installed on a similar vehicle.
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  • 2021 Chevy Equinox Diode Wiring Kit Installation
    The purpose of the diode is to prevent power from surging back and damaging your wires and other components. It sounds like the diodes are wired incorrectly if you're having issues with your signals flashing rapidly and giving you an error code on the console. You could also have a short somewhere in the wire if you accidentally nicked a wire while installing the diodes so you'll want to examine your wire to ensure there is no damage. I attached an installation video for the Roadmaster...
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  • Does Roadmaster Tow Bar Lighting Kit RM-15247 Fit 2021 Jeep Gladiator with LED Taillights
    Yes the Roadmaster tow bar lighting kit part # RM-15247 does fit your 2021 Jeep Gladiator with LED taillights. We have confirmed this with Roadmaster.
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  • Flat Tow Lighting Recommendation for 2002 GMC Yukon
    Hey Ron, so we have tow bar lighting solutions that will work great on your 2002 GMC Yukon but we don't have any that are plug and play. There's only a few vehicles that have that style of lighting available and due to the age of your Yukon there isn't one available. So instead you would want the Roadmaster diode kit part # RM-15247 which splices into your taillight wiring to allow the RV to control the vehicle taillights. The install is a little more involved but these kits are super...
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  • If Stop Light Fuse is Pulled on Vehicle is Brake Lite Relay Needed When Flat Towing
    I'd test the fuse solution first to make sure that the stop/turn signals of your vehicle do not come on at all when that fuse is pulled. If you will be using a diode kit for lighting like the part # RM-15247 which powers the taillights and the fuse being pulled does prevent the taillights from activating this would work well. This typically isn't recommended as basically you will be creating a kill switch for your brake lights...which is something that people looking for insurance money...
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  • Troubleshooting Weak Lighting Signals on Flat Towed 2008 Jeep Wrangler
    The issue you describe sounds like a classic grounding problem. Weak or loose grounds can cause all sorts of weird behavior from lighting circuits so I suggest you carefully check all wiring and connectors for grounding your towed Jeep Wrangler. Sometimes corrosion can develop in places where it is tough to spot, such as under a ring terminal or even inside a plug. Try removing the grounds and cleaning/sanding those grounding points thoroughly to remove paint, primer, rust, grease or even...
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  • Will Roadmaster Diode Kit RM-152497 Fit 1995 Geo Tracker and Work With Monaco Motorhome
    If your tow vehicle, the motorhome, has trailer wiring on it already it has the circuits combined as that is the standard way trailer wiring is ran. That means that for a diode wiring kit for your 1995 Geo Tracker the part # RM-15247 would fit and be exactly what you want without needing any further wiring or adapters.
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  • Estimated Install Time For Roadmaster Wiring Kit RM-15247 on 2007 Honda Accord
    Installation time can vary pretty significantly depending on the individual installing it, but a decent estimate is somewhere in the 2 hour range or so for a 2007 Honda Accord when installing the Roadmaster wiring kit you asked about: - Roadmaster Diode 7-Wire to 4-Wire Flexo-Coil Wiring Kit # RM-15247
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  • Tow Bar Lighting Kit Recommendation for 2020 Ford Expedition
    We don't have a tow bar wiring setup that fits your 2020 Ford Expedition that is plug and play but we do have great diode kit solutions like the Roadmaster part # RM-15247 which installs by splicing inline with the taillight circuits of your vehicle.
    view full answer...
  • Tow Bar Wiring Harness to Flat Tow a 2003 Chevy Silverado Behind an RV
    For tow bar wiring to flat tow your 2003 Chevy Silverado 1500 behind an RV I recommend the standard 4 diode kit # RM-154 if the RV has a 4-Way flat connector or # RM-15247 if it has a 7-Way connector. The diode kits are great because once installed you will not have to worry about it again. I have linked a video you can use as a guide for this installation.
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  • Flat Tow Wiring for 2015 Subaru Forester
    Both the Roadmaster Diode 7-Wire to 6-Wire Flexo-Coil Wiring Kit # RM-15267 and the 7-Wire to 4-Wire Flexo-Coil Wiring Kit # RM-15247 will work with your 2015 Subaru Forester so you can use either. The only difference between the two is that the 7-Wire to 6-Wire Flexo-Coil Wiring Kit # RM-15267 will provide you with a 6-way connector at the front of your Forester and # RM-15247 will give you a 4-way . Otherwise, the two operate exactly the same.
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    Image 1 for
  • Does Battery Need to be Disconnected to Install Roadmaster Flex-Coil Wiring Kit on 2019 Sierra 2500
    The Roadmaster Diode Flexo-Coil Wiring Kit # RM-15247 that you referenced will simply tap into the tail light circuits on your 2019 GMC Sierra 2500 so they can be powered in correspondence with the RV while flat towing. The installation of this system does not require the battery to be disconnected, but the owner's manual for your Sierra requires that this be done to flat tow the truck which is why we have it mentioned in our fit guide. GMC requires this so that the battery doesn't drain...
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  • Tow Bar Wiring Harness Recommendation for a 2016 Jeep Cherokee Trailhawk
    We have installed diode kits on Jeep Cherokee Trailhawks (and other models that have LED lights) and they have worked fine. For a diode kit I recommend # RM-15247. I have also included links to a couple of videos showing example installations. You can see the vehicles have the LED tail light assemblies like on your 2016 Cherokee. If your Cherokee has 4 wheel drive or the Active Drive II system, to maintain the vehicle's stable steering while being flat towed you will want to install the...
    view full answer...
  • Recommended Flat-Tow Wiring Harness for 2018 GMC Sierra 2500 and Is Brake Relay Needed
    The Roadmaster Diode 7-Wire to 4-Wire Flexo-Coil Wiring Kit part # RM-15247 is an excellent option for a 2018 GMC Sierra 2500 that will work well to illuminate the vehicle's tail lights using the motorhome. In regards to the Roadmaster Brake-Lite Relay Kit for Towed Vehicles part # RM-88400, this is not required for a 2018 GMC Sierra 2500.
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  • Wiring Kits Needed To Flat Tow A Ford F-150 Behind Another Truck
    You could install a diode wiring kit in the F-150, but the quickest and easiest route here would be to simply plug in some tow lights like the Roadmaster Standard Magnetic Tow Lights # RM-2120. If you are set on wanting to run the signals through the F-150's tail lights then you could use a universal diode wiring kit like the Roadmaster Diode 7-Wire to 4-Wire Flexo-Coil Wiring Kit # RM-15247. This kit will require you to splice into your F-150's wiring to complete the installation. Fitment...
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  • Where To Splice The Roadmaster InvisBrake Into The Tail Light Wiring Harness On A 2019 Jeep Wrangler
    The Roadmaster InvisiBrake Supplemental Braking System # RM-8700 can be spliced into trailer lighting harness before the diodes. Before meaning the wiring between the 4-pole connector and the diode. After being the wiring between the diode and the tail light. In the attached installation video (24 min. mark) Shane splices into excess wiring bundled up in the engine bay.
    view full answer...
  • Flat Tow Lighting Kit for 2021 Jeep Wrangler Unlimited and is Brake Lite Relay Needed
    For lighting for your 2021 Jeep Wrangler Unlimited you are going to want to go with a diode kit like the part # RM-15247 as there isn't a kit that installs into the vehicle taillight harness connections. From our research on your vehicle there isn't a brake lite relay required but you can test this by having your vehicle key turned off and then pressing the brake pedal. If the taillights don't come on you are good to not need the relay.
    view full answer...
  • Tow Bar Lighting Solution for 2001 Chevy Silverado
    For your 2001 Chevy Silverado there isn't a plug and play style of tow bar wiring available so your best option would be a diode kit like the part # RM-15247 which wires into the taillight wiring of your truck and allows the tow vehicle to control the truck's taillights.
    view full answer...
  • Can I Use A Universal Diode Kit On A 2020 Jeep Gladiator Rubicon?
    Hey John, we have not heard of any issues with the universal diode kits on a 2020 Jeep Gladiator Rubicon. All of our records show that you will not need any kind of relay. I recommend going with the # RM-15267 diode kit since it uses a 6-pin round plug for the front of the Jeep.
    view full answer...
  • Availability of Plug-In Tow Bar Wiring Kit for 2021 Jeep Wrangler Unlimited
    I recommend the Roadmaster Universal Hy-Power Diode Wiring Kit # RM-154 if you have an older motor home with a 4 pole connection. If you have a newer motorhome with a 7 pole connection I recommend the Roadmaster Diode 7-Wire to 4-Wire Flexo-Coil Wiring Kit # RM-15247.
    view full answer...
  • Recommendation on Wiring a 2015 Ford F-150 for Flat Towing
    On your 2015 Ford F-150, we have a couple options for you to choose when wiring your vehicle up for flat towing. The first option and most labor intensive would be to use the Roadmaster 7-Wire to 4-wire Flexo-Coil Kit # RM-15247. This kit includes the diodes and wire that will allow you to hard wire into your Ford's lighting wiring harness. You then would run the wiring to the front of the truck and install the 4- wire round plug. The 7-way to 4-way Flexo-Coil will connect your motor...
    view full answer...

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