1. Tow Bar Braking Systems
  2. Roadmaster
  3. Brake Light Relay
Roadmaster Brake-Lite Relay Kit for Towed Vehicles

Roadmaster Brake-Lite Relay Kit for Towed Vehicles

lowest price pledge
Retail:$51.80
Our Price: $41.58
You Save: 20%
Tow Bar Braking Systems
Orders above $99 qualify for Free Shipping
Shipping Weight: 0.53 lbs
Quantity: 
In Stock
Roadmaster Tow Bar Braking Systems - RM-88400
zoom in icon
slider vertical icon
zoom out icon
Comment field cannot be left empty.
Name field cannot be left empty.

Thank you! Your comment has been submitted successfully. You should be able to view your question/comment here within a few days.

Error submitting comment. Please try again momentarily.

Product Images

In Use/Installed

Customer Photos

Relay works with your tow bar wiring system to ensure that your towed vehicle's turn signal lights flash in tandem with your RV's lights. Lowest Prices for the best tow bar braking systems from Roadmaster. Roadmaster Brake-Lite Relay Kit for Towed Vehicles part number RM-88400 can be ordered online at etrailer.com or call 800-298-1624 for expert service.
  • All Info
  • Reviews (213)
  • Q & A (873)
  • Photos
  • Why etrailer?

Roadmaster Tow Bar Braking Systems

  • Brake Light Relay
  • Roadmaster

Relay works with your tow bar wiring system to ensure that your towed vehicle's turn signal lights flash in tandem with your RV's lights.


Features:

  • Keeps your towed car's brake signal from overriding the turn signal sent by your RV
    • Allows signal lights on towed car to flash in tandem with RV lights even when vehicle's brake pedal is depressed
  • Required on towed cars with combined lighting if you are using a supplemental braking system
    • Needed on applications with separate lighting if towed car is wired using a TrailerMate wiring harness or a 4-diode kit (instead of a 6-diode kit)
  • Does not interfere with towed car's electrical system
  • Activates automatically when RV running lights are turned on
  • Includes all necessary components for standard installation
    • May require additional connectors and length of wire for certain applications
  • Limited Lifetime Warranty


The purpose of a brake light relay kit is to prevent your towed car's brake signal from overriding the turn signal that comes from your RV. When your towed vehicle is properly wired and connected to your RV, its indicator lights will illuminate as you engage the turn signals in your RV. However, if you have only a four-diode system in place, the turn signal will be overridden by your towed car's brake signal as soon as your supplemental braking system presses the towed car's brake pedal. As a result, drivers behind you know only that you're slowing down and not that you are turning.


Installing a brake light relay in your towed vehicle fixes this problem by ensuring that your car's brake signal does not override the RV's turn signal. Therefore, your towed car's lights will function in accordance with your RV at all times.


Is a Relay Required?

To determine if a brake light relay is needed to properly wire your vehicle to be towed, answer the following questions.


Are you using a supplemental braking system that depresses the brake pedal in your towed car?

No - You do not need a brake light relay.

Yes - You may need a brake light relay. Continue on to the next question.


Do the brake lights on your towed car illuminate while the engine is off?

No - You do not need a brake light relay.

Yes - You may need a brake light relay. Continue on to the next question.


Do your towed car's brake lights act as both the brake signals and the turn signals?

No - You may need a brake light relay. Continue on to the next question.

Yes - Your towed car has a combined lighting system. You will need a brake light relay to ensure proper activation of its signal lights.


Does your towed car have separate brake lights and turn signals?

No - Your towed car has a combined lighting system. You will need a brake light relay.

Yes - Your towed car has a separate lighting system. You may need a brake light relay. Continue on to the next question.


Are you wiring your vehicle with a six-diode kit or a TowDaddy custom wiring harness?

No - You will need a brake light relay to ensure proper activation of your towed car's signal lights.

Yes - You do not need a brake light relay.


Installation of the Roadmaster Brake-Lite Relay

Most towed cars require the normally open installation method. Ford and Lincoln models with neutral tow kits and most automobiles that have a push-button start function will require the normally closed installation.


Normally Open

The diagram and steps shown below demonstrate the installation for normally open applications. Be sure to follow the instructions included with your relay kit for a more detailed process.


Standard Normally Open Installation for Roadmaster Brake-Lite Relay
  1. Remove the blue wire from the kit. This wire is not needed for normally open applications.
  2. Locate the brake-light-switch wire in your towed car.
  3. Remove the brake light fuse.
  4. Cut the brake light wire a few inches away from the "cold" side of the brake light switch.
  5. Attach the relay to the wiring for the RV braking monitor. The diagram above shows where the green wire attaches the relay to either a Roadmaster Even Brake or BrakeMaster system.
  6. Connect the black wire of the relay to the brake light wire near the brake light itself using the included blue butt connector.
  7. Identify a fuse that is only powered when the ignition is in the "run" position and not when it is in the "tow" position. Pull the fuse. Insert the fuse into the slot closest to the fuse blades, then insert the fuse tap into the empty slot in the fuse panel.
  8. Using the attached blue butt connector, connect the red wire from the brake relay to the wire from the fuse tap.
  9. Ground the white wire to your towed vehicle's frame.
  10. Secure the relay with the included wire ties.

Normally Closed

The diagram and steps shown below demonstrate the installation for normally closed applications. If you have a Ford or Lincoln that has a neutral tow kit or if your car has a push-button start feature that will not start the engine when the brake fuse is removed, then you need to perform a normally closed installation. Be sure to follow the instructions included with your relay kit for a more detailed process. Normally closed operations may require additional connectors and length of wire that are not included with this kit.


Normally Closed Installation for Roadmaster Brake-Lite Relay
  1. Remove the green wire from the kit. If you are using a Roadmaster Even Brake supplemental braking system, set this wire aside to use later.
  2. Locate the brake-light-switch wire in your towed car.
  3. Remove the brake light fuse.
  4. Cut the brake light wire a few inches away from the "cold" side of the brake light switch.
  5. Attach the relay to the wiring for the RV braking monitor. The diagram above shows where the blue wire attaches the relay to either a Roadmaster Even Brake or BrakeMaster system. The green wire may be needed here.
  6. Connect the black wire of the relay to the brake light wire near the brake light itself using the included blue butt connector.
  7. Use a voltmeter to identify the wire in your aftermarket light harness that is conducting the tail light signal. Typically, this is a brown wire.
  8. Using a 16 - 14 gauge butt connector (sold separately), attach a section of 14-gauge wire (sold separately) to the end of the red wire. Trim the new 14-gauge wire and connect it to your aftermarket wiring harness.
  9. Start your engine and turn on your headlights. Test the tail light wire with a voltmeter. If your voltmeter doesn't register any voltage, move on to step 10. If 12V DC registers, you will need to install a single diode (RM-790; sold separately).
  10. Ground the white wire to your towed car's frame.
  11. Secure the relay with the included wire ties.


88400 Road Master Brake Light Relay

Item # RM-88400

Installation Details RM-88400 Installation instructions




Customer Reviews

Roadmaster Brake-Lite Relay Kit for Towed Vehicles - RM-88400

Average Customer Rating:  4.7 out of 5 stars   (213 Customer Reviews)

Relay works with your tow bar wiring system to ensure that your towed vehicle's turn signal lights flash in tandem with your RV's lights.

- RM-88400
by:

I used this relay along with a separate switch to turn on Firestone air suspension compressor. Remember always use electric grease on connections. Thank you etrailer. God bless. Jesus saves.



- RM-88400
by:

Works as expected, with no problems. I am happy with etrailer and their customer interactions. I installed a Roadmaster tow bar and brakes on my Honda CRV two years ago. I had a problem and they helped me solve it with a new brake light relay kit. All parts of the install on the toad and motorhome are functioning perfectly.


Comments
Still working perfectly.
Hyatt - 05/16/2021


- RM-88400
by:

Evidently Roadmaster had made some slight alterations from the depiction, for the better. The fuse wiring was a spade end with two fuse holders built in. The holder closest to the spades was for the original circuit and the other for the new circuit. This was very handy. I had watched the installation video and thought it would be fairly easy; therefore I attached the terminals to the green, black, and white wires before even going to the CR-V. I did however purchase different spade connectors as I thought I may want to remove the brake relay switch in the future for another vehicle should I trade. Also the yellow connector is quite large and the video showed bending the wire over itself so that it would hold on the smaller wires. This was a wise decision. What was the problem was the wiring in my CR-V. The video showed similar size wiring from the brake switch. What I found was smaller wire, loomed very close to the brake switch. Evidently Honda had made some modifications. I believe the wire was 22 gauge and there was no real way the blue or yellow connectors would have worked. That said, after disconnecting from the switch, stripping the loom back to get some exposed wiring, cutting and using the 22-16 gauge connectors, drilling a hole for the ground screw, etc. the switch worked perfectly. I did vary the fuse location from the 7.5 Amp #29 Occupant Detection System (ODS) to the 15 Amp #28 Washer as I figured it would less likely interfere with any operation.


Comments
Working great with no problems.
Richard - 10/24/2018



- RM-88400
by:

The brake light relay kit has worked reliably for the year I've used it.



- RM-88400
by:

This can be a rather difficult installation for a do-it yourselfer but thanks to the etrailer instructions and video any handy person can accomplish it. Just make sure you watch the video and do it exactly as instructed. I downloaded the video to my laptop and put the laptop on the front seat of my F-150 so I could follow their step by step procedure and avoid doing any damage to my dashboard when disassembling it.


Comments
1 year out, still working great.
James D - 02/27/2021


- RM-88400
by:

From all of the positive reviews I'm sure this product works well for most people, but it didn't work well for me. Not much positive about this product except it did work after 2 days of trying to get the wiring sorted out. I ended up with two butchered wires because the installation instructions were incomplete and contained errors. I bought this for the plug and play since I could have bought all of the parts in the kit for less than $10 and figured out the wiring on my own, which I had to do anyway. Anyone with a 2010 Base Honda Fit should note that if you have a green/silver wire (kit instructions say to use for relay) and a green wire on a common terminal off the output of the brake light switch, you should be prepared to cut the green wire to install the relay. I can't say all are like mine because I understand that many have only the green/silver wire off the brake switch.


Comments
Since working through the installation problems, everything has been great. Although there were installation problems, they were worth it to have a simple hookup when towing.
Joseph S - 07/02/2020


- RM-88400
by:

I truly enjoy travelling with my MH and Roadmaster RM-88400 tow bar and braking system. I can stop wherever I like and unhook and be gone in 5 minutes. When finished site seeing or shopping I can be hooked up and on the road just as fast. Great system.


Comments
Great. The more I use it the better I like it. Takes a little time to figure out the process.
Bill M - 06/22/2020


- RM-88400
by: 04/08/2021

Self installed on 2018 Ford F150. Had issues due to cutting into very thin brake light switch wire. Bad connection created issue where truck would not come out of park. Use extra care when tapping into that wire. Also included fuse tap didn't work with 2018 F150. A micro mini fuse tap is required.



- RM-88400
by:

The installation video for the 2011 Honda CR-V was excellent and I used it to install the Brake-Lite Relay Kit on my 2012 CR-V. However, the picture of the kit at the beginning of the video was very misleading. It didn't show the fuse holder or the fuse talked about in the video, instead there was a yellow component pictured that had no relation to the installation or the actual kit that I received. Fortunately all the necessary parts were in the kit I received and the installation went just as the shown in the video. It works as described.


Comments
Ive towed the car for many miles and the relay still works perfectly.
John F - 07/24/2020


- RM-88400
by:

Not too hard, once wired right it's great. My advice, drop the provided blue butt connectors and use bell caps or something more reliable. Also the crimp on ring for ground was 1 size too small for my 2007 CRV. In the video for the 08 CRV the technition added an additional black wire to the brake unit. If you have an RVI3 brake you will not need the additional wire. If you use a brake system like an RVI3 wireless brake, this will keep blinkers blinking when braking.



- RM-88400
by:

I installed this on my towed vehicle about a year ago. The initial installation went well and the instructions provided the necessary information on installation. After a year, I have not had any issues with the equipment and the car's break lights work as expected as both a driven vehicle and a towed. There are a number of ways to setup a towed, and once I decided on using the vehicle lights rather than a light bar, this kit was kind of a no-brainer. Also, during the past 12 months I have purchased additional items from etrailer and have always been satisfied with both the products purchased and the support from etrailer.


Comments
The system continues to work as expected. We always perform a light check when hooking up the vehicle and have not had any issues with these components.
Robert M - 02/04/2020



- RM-88400
by:

This works perfectly and have driven several thousand miles with it. The installation did not work as specified. My model Jeep - a 2016 Cherokee with Active Drive II has two green wires with light green stripe, neither of which worked as the bypass. I tried it myself and took it to two mechanics; neither could find the correct wire or would attempt the work. I finally installed the relay in the fuse box. In my car, the brake light fuse is paired with the gas cap release in a micro3 (ATL) socket. This saves space in the fuse box for the manufacturer. The center pole is a shared hot for each of the two circuits. I installed a micro2 (ATR) fuse holder that has space for two ATR fuses (similar to the one supplied but has space for two fuses, not one). In the lower fuse holder socket, I installed a 10A fuse for the gas cap release. In the upper socket, I installed a 10A fuse for the the relay. I attached the blue relay wire to the red pigtail of the fuse holder. In the brake light side of the fuse box I installed half of an ATR fuse along with a tin fuse tap. I attached the black relay wire to the fuse tap. Finally I attached the red wire to the always hot wire on my 6-pin socket. This ensured that the relay is active as soon as I plug the Jeep into the motorhome. All the parts are available at a local auto parts store. Wiring this way took less than an hour, did not require cutting the brake light wire under the dash and *may* prevent voiding the warranty, although I did not verify this.



- RM-88400
by:

Great product that has everything needed for a simple install. Well, it is always interesting getting to the tiny wire on the brake light switch up under the dash, but I got it done!



- RM-88400
by:

Have a issue with 2016 Wrangler. Before install the brake light works anytime, even without key. After install the brake lights only work in the On/Run position (not in Accessory position). I use the Even Brake system which requires a brake signal, thus I have to set the ignition switch to On when I am towing which means the odometer will count the miles and who knows what could be damaged by leaving the ignition switch turned to On for several hours. This relay does exactly what it says, but I would prefer that it work in the Accessory position which is what is recommended in the Jeep manual for towing.



- RM-88400
by:

This review is for E-Trailer. I ordered a complete dinghy towing set-up for the dinghy as a towbar came with the RV we purchased. I called E-Trailer and spoke with a very knowledgeable young lady and when I told her what I needed in layman’s terms she came up with what I would need to complete the dinghy preparation in order to safely tow it behind our RV. Everything they said it would do went just as the instructions directed. I ordered a Roadmaster Falcon 2 set up for the dinghy and they suggested a Blue Ox self contained braking system for the SUV itself. hey also suggested the complete wiring system and plug for the dinghy. To my amazement after the RV and dinghy were connected that also was as easy as they said it would be. Our first tow with the dinghy was great and the unhooking was also a very easy experience. This company was awesome to work with. Thank you for your knowledge and great products.



- RM-88400
by:

I ordered all the parts required to safely flat tow out 2017 Jeep Cherokee Trailhawk from etrailer.com. The only part they didn't have was the Mopar Flat Tow Enhancement kit Jeep requires to flat tow this model. Ordering from them was great, the website is easy to use and I was able to locate all the pieces compatible with my specific vehicle. The expert recommendations help my decision choosing the right parts. I ordered from etrailer even though I found some of the parts on other websites a little cheaper. I chose to pay a little more because of all the effort etrailer has put into installation videos and guides. I was very pleasantly surprised to learn from etrailer that they have a price match guarantee! So my equipment consisted of the following Mopar Flat Tow Enhancement Kit (from Jeep) Roadmaster Battery Charge Line Kit for Towed Vehicles Mighty Cord 7-Way RV Style Trailer Connector - Trailer End WesBarg 7-Way, RV-Style Connector w/ 6' Long Coiled Cable Trailer End Pollak Black Plastic, 7-Pole, RV Blade-Style Trailer Socket - Vehicle End Hopkins Custom Tail Light Wiring Kit for Towed Vehicles SMI Stay-IN-Play DUO Supplemental Braking System Roadmaster Brake-Lite Relay Kit for Towed Vehicles Blue Ox Alpha Tow Bar - Motor Home Mount - 6,500 lbs Blue Ox Base Plate Kit - Removable Arms Blue Ox Tow Bar Cover - Aladdin, Aventa LX, Aventa II The installation videos are great but not all inclusive. Take the time to read the instructions that come with the parts. This is a major project, I took about 30 hrs over a full week but as you'll see in the pictures I took s few extra steps to make a cleaner look. Some of those extra steps: The base plate install requires the bumper be modified cutting off a flange on each side, I spray painted this to prevent corrosion. In the install video of the baseplate on the drivers side they use an extra quick link (not included) to run the safety cable around the wiper fluid reservoir. I took the time to remove it and run the safety cable behind it. I didn't want our nice new vehicle to look like it can be towed so I played the brake away switch and 7 way trailer plug behind the license plate, so when not being towed our vehicle looks great! Some things to be aware of. The Brake air cylinder that mounts to the brake pedal with four bolts may need longer bolts, it did on our Jeep. Spend the money for weather tight heat shrink crimp fittings. The Hopkins wire harness was about 1.5 feet short to get to my plug location. Buy extra zip ties, electrical tape and split loom. I recommend reading all the various installation manuals and watching all the videos because the various components integrate together and if you install one at a time you'll be doing a bunch of extra work. The brake light relay is a real pain in the butt, not because of the hardware but because of the location of the brake light switch which is very hard to get to. Overall I am very happy with the products and how the installation looks. We haven't towed it yet but do not expect any problems.


Comments
Still very happy with our purchase. We’ve towed over 10k miles and have had zero issues with our tow setup. I’ve shared my experience with several other RVrs and recommended your company for their needs. Thank you
Roy - 07/30/2018



- RM-88400
by:

Pulled entire length of route 66 and then some. We had absolutely no issues with all of our etrailer equipment. Thanks for all of your help.



- RM-88400
by:

I have a 2016 Jeep Wrangler Sport Unlimited 4 door, after I installed the Hopkins Custom Tail Light Wiring Kit for Towed Vehicles - HM56200, I found I had to install the Road-Master Brake Lite Relay for Towed Vehicles - RM-88400 , I'm using a supplemental brake system, when the brake is depressed with ignition off, the brake lights come on and cancel out any directional signal on my toad, installing the relay solved this problem. I watched the video and this was helpful. Installation took me a few hours, climbing under the dash was not an easy chore for me, I'm not as young as I want to be, had to purchase 16 gauge Red wire to run to Fuse box under the hood, also I recommend having extra wire ties to do this. I recommend both products, easy to install and good quality.


Comments
Products are working well, have not had any problems with the system
Rich L - 11/13/2017



- RM-88400
by:

I have now installed the following on my 2017 Wrangler: Brake light relay kit . Hopkins Towed vehicle Tail Light wiring kit. Blue Ox base plate. Blue Ox Patriot Portable RF Braking System. All of this has taken about 3 days of work spread out over a week or so. Overall it went well. Not too many surprises. Crawling around under a car at 71 is a bit of a strain but I'll get over it. I must say that Donna P. has been a wonderful source of great information and has stayed right on top of the process. eTrailer has been a great source for this project. I would recommend you all with no hesitation.


Comments
I am still in love with the products. My only issue is having enough time to use them more.
John M - 06/15/2018



- RM-88400
by:

Relay works as advertised - cuts power to my 2013 Edge brake lights (with the key in the off/or accessory position) preventing the Edge brake lights from overriding the coach brake/turn signals when my supplemental braking system pulls the Edge brake pedal down. Bit of a chore to install, mainly due to close quarters under driver's side of lower instrument panel and forced to lay half way in/out of Edge over the door sill. Also, vehicle info on Roadmaster web site indicates the Edge brake light wire coming from switch is purple/white, but I found 2 purple and white wires on mine, both together in the same socket on the brake light switch. Guess it depends on one's color sensing, but one of mine was a lighter shade of purple and the other darker, more shiny. I spliced into the light purple one first and naturally it was the wrong one, so had to reconnect it and splice into the other one to make everything work. Not a biggie, but the mini fuse tap supplied in the kit will not work with the low-profile mini-fuses used in the Edge interior fuse panel - you have to use a regular mini-fuse. FYI - 2013 Edge Limited, V6/FWD; Air Force One supplemental brake system; DEMCO RV Tow Harness wiring kit (9523100) for tail/brake light connections (plug in/no splicing); DEMCO baseplate and Blue Ox Towbar.


Comments
John, do you have to pull fuses in your Edge? If so, which fuses do you pull?
-- comment by: Mike H - 04/22/2014

The 2013 Ford Edge doesn't require a fuse to be pulled, but doing so will eliminate the need to cycle the engine. If you pull MAIN IGNITION # 28 in the driver footwell fuse box, you can skip the starting and running procedure at the end of the tow. To do this you can either the fuse to be removed or to install a fuse bypass switch like part # RM76511
Roadmaster FuseMaster Fuse Bypass - 13" - 20-Amp Mini-Fuse
$91.98
. If you don't pull or bypass this fuse, you will need to follow the engine start procedure Ford outlines in the manual. Ford also indicates in the manual that if the Edge is a 2.0L 4 cyl. you must use a tow dolly to keep the front wheels off the ground, no flat tow. If it is a 3.5L or 3.7L V-6, you can either flat tow with all 4 wheels down or on a trailer. No tow dollies with front up and rear down.

-- Etrailer Expert Patrick B - 4/23/2014


- RM-88400
by:

Worked out great just not easy for an old man to get under dash to install. I really like that e trailer has videos showing install of their products.



- RM-88400
by:

Had to get help from etrailer in this but eventually got it done



- RM-88400
by:

worked like a charm, instructions well done



- RM-88400
by:

Justin B. was extremely helpful, answered my questions & checked the vehicle model to find I also needed a brake light relay. The shipping was on time also. Great place to deal with. Thanks Justin



- RM-88400
by:

Good quality. Good instructions. Difficult to install only due to the tight quarters inside the Jeep. Works great.


28
216
Show More Reviews

Ask the Experts about this Roadmaster Tow Bar Braking Systems

  • Is Roadmaster Brake-Lite Relay Needed for Flat Towing 2020 Jeep Wrangler with Push Button Start
    The Roadmaster Brake-Lite Relay # 88400 that you referenced actually isn't needed for your 2020 Jeep Wrangler Unlimited with the push button start. In order to ensure proper operation of the signal lights and braking system you instead need the Stop Light Switch Kit # RM-751490. I have attached the written installation manual below along with an install video that you can follow along with.
    view full answer...
  • Blue Ox Base Plates & Parts to Flat Tow 2021 Ford F-250 Super Duty
    We have you covered with all the parts you'll need to flat tow your 2021 Ford F-250 Super Duty, including the Blue Ox base plates. These are a really nice choice because there isn't any part of the base plate showing except for the tabs, which are removable when you aren't flat towing your truck, which ensures it keeps it's aesthetic. The list of all the parts you need to flat tow your 2021 F-250, including the base plates, is the following: - Base Plate Kit: Blue Ox Base Plate Kit...
    view full answer...
    Image 1 for
  • How To Wire the Hopkins Flat-Tow Harness and Roadmaster InvisiBrake Toghter On a 2016 Jeep JKU
    For starters, there is no bridge between the toad and the tow vehicle for the Roadmaster Brake-Lite Relay Kit for Towed Vehicles part # RM-88400. This gets installed solely on the toad. In regards to the Hopkins Custom Tail Light Wiring Kit for Towed Vehicles part # HM56200, the Roadmaster InvisiBrake Supplemental Braking System part # RM-8700, and the RoadMaster 7-Wire to 6-Wire Flexo-Coil Kit part # RM-146-7 there are going to be components that gets bridged to the tow vehicle. The...
    view full answer...
    Image 1 for
  • Does The 2021 Jeep Wrangler Unlimited Need A Brake Light Relay For Flat Towing
    No, the brake light relay Item # RM-88400 is not used for the 2021 Jeep Wrangler Unlimited because the brake wire cannot be spliced into. Instead you would want to use the Roadmaster Stop Light Switch Kit Item # RM-751490. Now you would only need this if you are using a permanently installed braking system. If you are using a portable system then you would not need it.
    view full answer...
  • Can Brake Lite Relay be Used with Hopkins Tow Bar Lighting for 2008 Jeep Wrangler Flat Towed
    Yes the Brake Lite Relay part # RM-88400 does fit with the Hopkins tow bar wiring kit part # HM56200 that you have. This is a required relay solution if you are using supplemental braking that depresses the brake pedal of the vehicle and your taillights come on with the vehicle off.
    view full answer...
  • Why is Stop Light Switch Needed on 2020 Jeep Wrangler Unlimited
    The reason you need the Roadmaster Stop Light Switch Kit # RM-751490 and not the Brake-Lite Relay #RM-88400 on your 2020 Jeep Wrangler Unlimited is because on some vehicles, the brake light switch is activated electronically, so there's no way to truly tap into it. The Stop Light Switch Kit will provide that signal in place of the OEM signal, so you will need it with the Blue Ox Patriot 3 Radio Frequency, Portable Braking System # BRK2019, along with 12 Volt Outlet Kit # RM-9332. Additionally,...
    view full answer...
  • How to Determine if Vehicle Needs Brake Lite Relay when Flat Towing
    To determine if a brake light relay is needed to properly wire your vehicle to be towed, answer the following questions. Are you using a supplemental braking system that depresses the brake pedal in your towed car? No - You do not need a brake light relay. Yes - You may need a brake light relay. Continue on to the next question. Do the brake lights on your towed car illuminate while the engine is off? No - You do not need a brake light relay. Yes - You may need a brake light relay....
    view full answer...
  • Installation of Diode In Roadmaster Brake Light Relay Kit on 2020 Ford F-150
    If you have a Ford or Lincoln that has a neutral tow kit or if your car has a push-button start feature that will not start the engine when the brake fuse is removed, then you need to perform a normally closed installation which involves using a diode-which I believe is the process you're referring to. I've linked a photo that shows the diode installation when using the Roadmaster Brake Light Relay Kit # RM-88400 that you can refer to, but you will splice into the brown wire on the...
    view full answer...
    Image 1 for
  • Installation of Roadmaster Brake-Lite Relay
    It sounds like the Roadmaster Brake-Lite Relay Kit for Towed Vehicles # RM-88400 has possibly gone bad; if there was enough current to blow a fuse, it's possible that it also caused the relay to go bad. There are detailed instructions linked to this answer and you'll need to determine based off the vehicle you're towing whether or not you will install it normally open or normally closed- there are also diagrams and instructions on the product page.
    view full answer...
  • Troubleshooting Roadmaster Brake-Lite Relay Kit on 2015 Jeep Cherokee
    I spoke with my contact at Roadmaster regarding the issues you are having with the Brake-Lite Relay Kit # RM-88400 on your 2015 Jeep Cherokee. There are a couple possible reasons for why you are having trouble with the push-button start and also the cruise control in your vehicle. First, he said to just verify that when installing the kit, you followed the "Instruction Sheet B" in the included installation manual. This refers to the installation instructions for vehicles that have a...
    view full answer...
    Image 1 for
  • Converting 6-Way of Trailer to 7-Way to Connect to 2003 GMC Sierra 2500HD
    Whenever possible I recommend avoiding adapters if they aren't needed as it's another connection point that can cause issues. Since the 7-way connector is much more common than the 6-way I would recommend replacing the 6-way on your trailer with a 7-way that matches your vehicle directly. Easy solution for that is the part # A10-7081VP. I attached a diagram for 7-ways for you to check out as well as one for a 6-way to help make the transition easy.
    view full answer...
    Image 1 for Image 2 for
  • 2018 Jeep Wrangler Unlimited Sahara JL Wiring for Flat Towing
    For your 2018 Jeep Wrangler Unlimited Sahara JL flat tow wiring, you will need the Roadmaster Stop Light Switch Kit # RM-751490 which will communicate with your motorhome's brake monitoring system that your Jeep brakes are being applied. This is to help you know if a problem is occurring like your Jeep brakes constantly being applied so you can solve an issue before damage occurs. I reached out to my tech contact at Roadmaster and you will not need the relay # RM-88400 because the factory...
    view full answer...
    Image 1 for
  • No Brake Lights With Ignition Off Using Roadmaster Brake-Lite Relay Kit On a 2010 Honda Fit
    I spoke with Roadmaster about the issue you are having with the Roadmaster Brake-Lite Relay Kit for Towed Vehicles part # RM-88400 on your 2010 Honda Fit. They informed me that if the brake lights do not illuminate while the brake pedal is pressed when the vehicle's ignition is off then the relay is wired incorrectly so you will need to review that portion of the installation instructions which I have attached for you. If you think the relay is bad then you can switch this out for just...
    view full answer...
    Image 1 for
  • Where Does Roadmaster Brake Lite Relay # RM-88400 Install
    I attached a diagram that shows where all of the connections of the Brake Lite Relay part # RM-88400 need to be made. Basically the 85 pin gets grounded, 87 gets ran to brake light switch and signal output, 86 runs to a fuse tap, and 30 runs to the brake light wire. I also attached an install video for this kit for you to check out as well. Here's an instructions overview for more info. Remove the blue wire from the kit. This wire is not needed for normally open applications. Locate...
    view full answer...
    Image 1 for
  • Is Brake-Lite Relay Kit 88400 Needed for a 2019 Jeep JL Wrangler with Push Button Start
    The Roadmaster Brake-Lite Relay Kit # RM-88400 actually isn't needed on your 2019 Jeep JL Wrangler. Instead what you need to ensure that your lights are working is a stop light switch. We have the Universal Stop Light Switch Kit # RM-751000 or the Custom Stop Light Switch Kit # RM-751490 for you to use. I confirmed this with my contact at Roadmaster. For a complete flat towing setup you will also need a base plate kit, tow bar, safety cables, vehicle tow bar wiring, a supplemental braking...
    view full answer...
  • Will the Stop Light Relay Be Needed When Using Supplemental Braking on a 2015 Jeep Wrangler
    Yes, if the supplemental braking system uses the brake pedal to apply your 2015 Jeep Wrangle's brakes, then you will need to wire in the Roadmaster Brake Relay, # RM-88400. The relay will keep your Jeep's brake light signal from overriding the turn signal coming from your RV. The will bypass the brake signal to allow which every turn signal you have on to not stop blinking when the brakes are applied. I have attached an installation video that will show this relay being installed...
    view full answer...
  • Does Flat Towing 2016 Chevy Equinox 4 Cylinder Require Brake-Lite Relay
    Thank you for the purchase of the Hopkins Custom Tail Light Wiring Kit for Towed Vehicles # HM56108 though I checked with Roadmaster and your 2016 Chevy Equinox does not require the Brake-Lite Relay # RM-88400. There are a number of requirements to flat tow your Equinox, though this relay is not one of them. Fuses need to be pulled so you will need the Roadmaster FuseMaster Fuse Bypass Switch for Towed Vehicles - 50-Amp FMX Fuse # RM-76517 and Roadmaster Battery Charge Line Kit for Towed...
    view full answer...
  • Can Brake Light Relay RM-88400 Be Installed on a 2018 Jeep JL Wrangler Unlimited
    The problem with the 2018 Jeep JL Wranglers is that the circuit you need to install the brake light relay # RM-88400 is inaccessible but it isn't required on this vehicle. When your JL Wrangler is set up in flat tow mode (see owner's manual) the brake light circuit is not active. That is why we do not list it for that particular vehicle. When in flat tow mode it will work fine. Or you can avoid all together by going with either magnetic light kit # C-ATL20A or EZ Mount kit # EZT20B....
    view full answer...
  • Recommended Items Needed When Flat-Towing 2002 Jeep Wrangler
    When flat-towing a vehicle like your 2002 Jeep Wrangler behind your motorhome, there are 5 items needed. You will need base plates, a tow bar, safety cables, wiring for the towed vehicle and most states now require a supplemental brake system. Just in case you do not have all of these items I will make some recommendations that will work for you. For base plates I recommend the Roadmaster XL Base Plate Kit, part # RM-521424-4 if you have a double tube. These feature a hidden bracket...
    view full answer...
  • How to Determine if a Brake Light Relay is Required to Flat Tow a Vehicle
    To determine if your 2014 Jeep Grand Cherokee will require a brake light relay like part # RM-88400 you need to answer the following questions: Are you using a supplemental braking system that depresses the brake pedal in your towed car? No - You do not need a brake light relay. Yes - You may need a brake light relay. Continue on to the next question. Do the brake lights on your towed car illuminate while the engine is off? No - You do not need a brake light relay. Yes...
    view full answer...
  • Is the Roadmaster Brake Lite Relay Required to Use Blue Ox Patriot 3 on 2016 Jeep Wrangler Unlimited
    We do appreciate your patronage in the past, so thank you for that. To answer your question, the answer is-Yes. The Roadmaster Brake Lite Relay # RM-88400 is required for any braking system that physically pushes on the brake pedal like what the Patriot 3 # BRK2019 does. I've linked an installation video of the relay kit on a similar 2016 JKU for you to have a look at.
    view full answer...
  • Instead of Brake Light Relay for Flat Towing Could Vehicle Battery Be Disconnected
    If you wanted to kill the power to your vehicle battery so that it wouldn't activate the brake lights when the supplemental braking system presses the brakes that would be one option. To power the supplemental braking system you could then use the part # RM-9332 for an outlet kit. You could use the # DW05312 as a battery disconnect.
    view full answer...
  • Is a Brake Light Relay Required for Installation of Flat Towing Lighting on a 2013 Lincoln MKX
    The Hopkins Tow Bar lighting kit part # HM56002 has been confirmed as a fit for your 2013 Lincoln MKX so it would work well for you. To determine if a brake light relay # RM-88400 is needed to properly wire your vehicle to be towed, answer the following questions. Are you using a supplemental braking system that depresses the brake pedal in your towed car? No - You do not need a brake light relay. Yes - You may need a brake light relay. Continue on to the next question. Do...
    view full answer...
  • Recommended Parts Needed to Flat Tow a 2010 Honda CR-V Behind a Motor Home
    To flat tow your 2010 Honda CR-V behind a motor home you will need base plates, a tow bar, safety cables, lighting, and supplemental braking. The base plates will provide the proper safe and secure attachment point for the tow bar on your CR-V. The Blue Ox base plates # BX2246 tend to install a little easier so I recommend them for your CR-V. There are several compatible tow bars but the one I recommend the most often is the Alpha, # BX7380. The Alpha has a 6,500 pound capacity...
    view full answer...
  • Is Brake Light Relay Needed When Flat-Towing 2013 Honda CR-V
    The Roadmaster Brake-Lite Relay Kit, part # RM-88400 is used when you have combined lighting on your towed vehicle and want to use a supplemental brake system. The easiest way to find out if you need a relay is to turn the engine off and when pushing the brake pedal see if the brake lights come on. If they do, then a brake relay switch is needed. from my research it does not appear you need a brake light relay on your CR-V, but you can check to make sure. When towing your CR-V, the Roadmaster...
    view full answer...
  • Installation Instructions for Roadmaster Brake Lite Relay and Brakemaster 9000
    There are two methods of installation for the Roadmaster Brake Lite Relay part # RM-88400 that you referenced, open and closed. Most towed cars require the normally open installation method. Ford and Lincoln models with neutral tow kits and most automobiles that have a push-button start function will require the normally closed installation. Check out the diagram that details the installation. Remove the blue wire from the kit. This wire is not needed for normally open applications. Locate...
    view full answer...
    Image 1 for Image 2 for
  • Installing Brake Relay Switch On 2013 Jeep Wrangler Unlimited For Flat Towing Behind Relay
    When installing a supplemental brake system on your 2013 Jeep Wrangler Unlimited, you will need to add a brake relay kit. If no kit is used you can have all kinds of unpredictable results. I recommend the Roadmaster Kit, part # RM-88400. I have attached a drawing that shows how this is to be installed on your system. There are 4 wires that are attached to the relay. Use a circuit tester like part # 40376 to find the right wires. The Green wire connects to the cold side of the vehicle...
    view full answer...
    Image 1 for
  • Turn Signal on 2016 Jeep Wrangler Stops Working When Brakes are Applied on RV
    The solution for your 2016 Jeep Wrangler flat towing situation is the RoadMaster Brake-Lite Relay Kit # RM-88400. The Brake-Lite Relay Kit will keep the your Wrangler's brake signal from overriding the turn signal which comes from your RV. I have attached a demonstration video of this relay kit being installed on a similar 2016 Jeep for you to use as a reference.
    view full answer...

Do you have a question about this Tow Bar Braking System?




  • Why etrailer.com?

    At etrailer.com we guarantee:
  • Highest quality tow bar braking systems for the best price.

    Our Lowest Price Pledge ensures you will never overpay for the parts you need.
  • Real product know-how.

    We make sure that the products we sell are what we say they are, and that they work the way they are supposed to work. Get real advice from a real person who has the knowledge and expertise needed to solve your problem.
  • Most detailed, accurate tow bar braking system information available.

    Because we take providing accurate product information seriously, we take our own detailed product photos, demo videos and installation videos, as well as verify measurements, instructions, and vehicle fit information.
  • Installations, made easy.

    We love helping people and have the most highly-trained customer service, hands-on experience, step by step videos and installation instructions.
  • Fast shipping.

    Your order is automatically routed to get out of our warehouse and to your door as quickly as possible. Receive free shipping on orders over $99.
  • Personalized service for life.

    We provide one-on-one, personalized service from the ordering process through the life of your product.
  • Trusted since 1946.

    We've been serving customers since our parts store first opened in 1946 and continue to be recognized by our customers, our vendors and third parties for exceptional service.
  • Returns Policy

    Need to return an item? No problem. Please read our Returns Policy for more information.

Info for this part was:

Employee Joe V
Test Fit:
Joe V
Employee Randy B
Test Fit:
Randy B
Employee Brent H
Test Fit:
Brent H
Employee Shane H
Test Fit:
Shane H
Employee Robert C
Test Fit:
Robert C
Employee Conner L
Test Fit:
Conner L
Employee David F
Test Fit:
David F
Employee Ryan G
Test Fit:
Ryan G
Employee Clayton O
Test Fit:
Clayton O
Employee Mike L
Expert Research:
Mike L
Employee Michael H
Expert Research:
Michael H
Employee Jameson C
Expert Research:
Jameson C
Employee Adam R
Expert Research:
Adam R
Employee Jeffrey L
Expert Research:
Jeffrey L
Employee Zack K
Video Edited:
Zack K
Employee Joshua S
Video Edited:
Joshua S
Employee Jacob T
Video Edited:
Jacob T
Employee Andrew L
Video Edited:
Andrew L
Employee Dustin K
Video Edited:
Dustin K
Employee Sue W
Video Edited:
Sue W
Employee Chris R
Video Edited:
Chris R
Employee Zach D
Video Edited:
Zach D
Employee Andrew K
Video by:
Andrew K
Employee Kathleen M
Video by:
Kathleen M
Employee Alan C
Video by:
Alan C
Employee Jonathan Y
Video by:
Jonathan Y
Employee Michael B
Video by:
Michael B
Employee Lindsey S
Written by:
Lindsey S
Employee Cole B
Installed by:
Cole B
Employee Shelly K
Updated by:
Shelly K
Employee Wilson B
Updated by:
Wilson B
Employee Isabelle B
Updated by:
Isabelle B

At etrailer.com we provide the best information available about the products we sell. We take the quality of our information seriously so that you can get the right part the first time. Let us know if anything is missing or if you have any questions.


Product Experts Available Now!
Call 800-298-1624