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Roadmaster Brake-Lite Relay Kit for Towed Vehicles

Roadmaster Brake-Lite Relay Kit for Towed Vehicles

Item # RM-88400
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Roadmaster Tow Bar Braking Systems - RM-88400
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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 800-298-8924 for expert service.
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Roadmaster Tow Bar Braking Systems - RM-88400

  • 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

Installation Details RM-88400 Installation instructions




Customer Reviews

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

Average Customer Rating:  4.8 out of 5 stars   (120 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 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. 602324


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

65265

- RM-88400
by:

I ordered an entire setup to flat tow my Subaru with my RV. Having never done this before I was nervous about missing something I might need. etrailer made it very easy when I called them on the phone. I told them what I was trying to do and they made sure I had everything needed to complete the job. I was given a name and phone number to call the same person if I had any issues. When one of the boxes was opened it was missing two pins from the manufacturer. A quick phone call and they had them in the mail in a matter of hours. This kind of personalized service is missing in our ever changing world. It was a pleasant surprise to find it here. Great Job etrailer. I will favorably recommend to everyone. 493271



- RM-88400
by:

I found this much more difficult to install than I expected. 2012 Jeep Wrangler. Reguired me "standing" on my head working with short wire connections where a mistake or need to rebare a wire was tough. Original mistake was using type of harness which required this. In hindsight would have gone with complete harness ( with bulbs) and completely bypassed the jeeps own lights 363067



- 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. 124112


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

3665

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
$90.31
. 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.

-- Patrick B - 4/23/2014


- 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. 413529


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

41671

- RM-88400
by:

Instructions were perfect and easy to follow. Highly recommend! 808963



- RM-88400
by:

Excellent product. It is well built, durable and easy to connect and disconnect. The LED lights on the sides are also a great safety feature. I recommend getting the cover to protect it from the elements when not in use. 807224



- RM-88400
by:

Great product and value 808210



- RM-88400
by:

Great product, easy instructions. Works as advertised 808203



- RM-88400
by:

Installed per instruction had one minor question support from etrailer was prompt and excellent 804587



- RM-88400
by:

So Happy Here!!! Fair price, Great Quality, Everything fit perfectly and looks Great on my Grande Cherokee 804069



- 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. 800384



- RM-88400
by:

Works good 794222



- RM-88400
by:

Works as advertised. 793985



- RM-88400
by:

Works as it should. 783046



- 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. 783037



- RM-88400
by:

Easy install, and beats aux. lights, no more bolt/unbolt of lights and looks soo much better. 777208



- RM-88400
by:

I recommend watching the etrailer video first, it will make the installation much easier! 769481



- RM-88400
by:

As always etrailer was super fast at filling my order. 762792



- 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. 758860



- RM-88400
by:

Easy to install. Took awhile for me to understand installation but working well a year later 754941



- RM-88400
by:

We are very happy with our towing equipment. We have used it a lot this past year with zero problems. 736886



- RM-88400
by:

Easy installation into 2007 CRV. Seems to work fine over the past year. 717472



- RM-88400
by:

Same as with the review of the wiring harness, this was done at a trusted repair shop. I took it there, as I had run out of time to do it at home. I am glad I did. It can be done at home, but it was a much bigger job than I or my trusted mechanic friend had expected. He did an excellent job with the advantage of a lift, a shop full of tools, and a lot of mechanical experience. Now that it is in and has 1,000+ miles on it, it is a really nice set up. 715408



- RM-88400
by:

Cailee was great to work with! 696608


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  • Where Does Roadmaster Brake Lite Relay # RM-88400 Install
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  • Is Brake Light Relay Used w/Patriot Braking System and Hopkins Wiring for a 2017 Jeep Cherokee
    There were special instructions for the 2014 and 2015 Jeep Cherokee regarding the brake light relay and braking systems but not for the 2017 models. One sure way to avoid having to use the relay, which is # RM-88400, is to use a magnetic light kit such as # C-ATL20A. All other light kits will require the use of the relay. Otherwise, since your Jeep has a push-button start feature, you would follow the Normally Closed part of the instructions for the relay. The relay is listed as required...
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  • Is Brake Light Relay Required with Blue Ox Patriot System on a 2017 Jeep Wrangler Unlimited
    On the 2017 Jeep Wrangler Unlimited the brake light relay # RM-88400 is required to prevent the towed vehicle's brake signal from overriding the turn signal from the RV when applying the brakes during a turn. But if you were to use a light kit such as # EZT20B or # C-ATL20A then it is not required. With any other light kit you would need to use it.
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  • Installation of Demco SMI Air Force One Braking System on 2015 Ford F-150 with Push Button Ignition
    The SMI Air Force One Supplemental Braking System for Motor Homes with Air Brakes - Proportional # SM99243 does not need any additional diodes for installation. I double checked with my tech contact at SMI Demco and it will install in the exact same way as a keyed start vehicle so no diode is needed. You will still need the Roadmaster # RM-88400 relay to prevent the towed vehicle's brake signal from overriding the turn signal from the RV when applying the brakes during a turn but nothing...
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  • Does a 2011 Jeep Wrangler Unlimited Require a Brake Light Relay when Being Flat Towed
    To determine if your 2011 Jeep Wrangler Unlimited needs a brake light relay, there are three things to consider. All three of these have to be true for your vehicle to necessitate a brake light relay. If you use the towed vehicles brake light as both the brake signal and the turn signal for towing (combined system); if a supplemental braking system that either pushes or pulls on the brake pedal has been installed; and with the ignition off, the towed vehicles brake lights illuminate...
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  • When is the Brake-Lite Relay Part # RM-88400 Required for a 2013 Jeep Wrangler
    Yes, the Roadmaster Brake-Lite Relay Kit for Towed Vehicles part # RM-88400 will be required for your 2013 Jeep Wrangler even if you are using the Roadmaster Diode 7-Wire to 6-Wire Flexo-Coil Wiring Kit part # RM-15267. The only time that the brake-light relay is not required is when you are using a set of magnetic tow lights like the Heavy Duty Magnetic Tow Lights part # TL21RK. The brake-light relay is designed to prevent the towed vehicle's brake signal from overriding the turn signal...
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  • Installing Brake-Lite Relay Kit # RM-88400 & Tail Light Wiring Kit # RM-155 on a 2016 Chevy Sonic
    The Brake-Lite Relay Kit # RM-88400 is really only used when you will have trouble seeing the turn signal over the brake lights on your vehicle. If you check out the installation of the Tail Light Wiring Kit # RM-155 on a similar 2016 Chevrolet Sonic you can see that there is room in the part of the assembly that has the clear lens for the extra bulb so you shouldn't have trouble seeing your turn signal at the same time that your brake signal is activated. With that being said, if you...
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