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Roadmaster/
Brake Light RelayItem # RM-88400
Retail:$51.38
Our Price: $29.95
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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.
Features:
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.
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.
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.
Installation Details 
Video of Roadmaster Brake-Lite Relay Kit for Towed Vehicles
Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.
Average Customer Rating: 4.7 out of 5 stars (95 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.
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
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. 316372
Products are working well, have not had any problems with the system
Rich L - 11/13/2017Relay 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
John, do you have to pull fuses in your Edge? If so, which fuses do you pull?
-- comment by: Mike H - 04/22/2014The 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
$58.38. 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 - 4/23/2014I 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
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 - 07/30/2018etrailer has been fantastic to work with...email 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 base plate 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 545375
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. 445760
Working great with no problems.
Richard - 10/24/2018I 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
Relay works as described. your video installation in a 2016 jeep JK was great. product has an improved fuse box mount that is better than what is shown in the video. I also drilled a wire sized hole in the side of the fuse box on the fender side of box to run the power wire thru instead of cutting a chunk out as you did in the video. etrailers total shipped price was lower than XXXXXXX. 314713
The Jeep Wrangler video was very helpful for the installation process. It should be updated to include the new type fuse holder. As with most vehicle repairs, having the correct tools for the job is very important. 472802
Installed this along with a brake light diode kit. Watched the videos a few times to figure it all out. The instructions it comes with are too complicated for my simple brain. Took me about an hour or so to install as I had to take out my front seat to get access under my dash. I have 2012 wrangler unlimited and its tight under there. After it was all installed I tested it and it worked great. Thank you! 195133
My 2015 Jeep Wrangler needed this harness to enable the turn signal and break lights to work correctly when I was towing it. The Roadmaster brake lite Relay hit did the job for me. It was relaticely easy to isntall and the directions and support helped me get it done quickly and easily. 256154
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. 396394
I am still in love with the products. My only issue is having enough time to use them more.
John M - 06/15/2018Great kit, easy to install! 651768
Great product. Easy to install. 644020
Have towed my truck over 6,000 miles and still working great. 642146
Easy to install and works as intended. 641116
Everything is doing very good. 635111
As advertised 633788
I am very please with the products I have received from etrailer. I hope no problems at all 627816
Great product The electrical hook up was changing 621620
Worked very well. 608071
Installed easily. Works great with my towed vehicle. 608436
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. 601731
Ground end does not fit over factory ground bolt on left side wall of foot well. Used self tapping screw included but not as clean as using the factory bolt. Otherwise great product. 600592
Great support and video's. Product are top notch with lots of information on the products, Thanks 580266
The Roadmaster Brake-Lite Relay kit works good and easy to install 578570
I ordered base plate, tow bar and all the goodies to hook up to our RV. Very good service and everything was delivered in 3 days. In the process of installing now. I have ordered parts from etrailer before and they have always been very good. 574632
Product was as advertised. Quick turn around from order to delivery! 568030
I open the package and all looks correct, have not yet installed on Jeep Again Great service from Etrailer!! 554325
The product performs as advertised. Etrailer video was more helpful than the general Roadmaster paper instruction. Except for tight fit getting both hands under the steering column--the job took less than 30 minutes and works like a charm. Perfect companion to previously installed Hopkins HM56200 light kit--also went in easy--just plug and play. thanks 554309
Very happy with etrailer for the purchase of a Blue Ox tow bar with needed hook ups for lights, etc and an Air Force One Brake system for my 2018 F150. Crystal did a great job of comparing options and matching pricing from across the web. She offered free installation. The Installer, Shane was awesome, I wanted all hookups hidden by the front plate on the F150 when not towing, Shane came through and then some. Finally, the manager Robert was excellent on follow-up as we had some air leak once we got home. etrailer stood behind everything and follow was exceptional. Very pleased! 553941
easy hook up great vidio for help thx... 524130
Works like etrailer said it would. Good advice and instructions 518351
The product arrived on time. With step by step instructions, it was simple and easy to install. I've had no problems with this setup and am still using it today. Thank you etrailer. 513845
Easy installation. Product works great. 501366
Excellent service 497735
Came right to door in promised time. Being installed as I speak. Will update after installed and tested. 493331
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
Innovative product. Excellent instructions. Fast shipping always appreciated. Thank you. Installed on 99 Chevy Tracker we pull behind a 2005 Coachmen Class C. Also have Roadmaster base plate and tow bar. Excellent products. Installing RM-15267 Wiring Kit soon. Been using magnetic lights on rear roof. Only question now is how to find our Tracker in Walmart parking lot without mouse ears in back. 486271
I followed the instructions carefully and made sure I fully understood how the circuit worked. The only problem I had was the supplied red wire was too short to reach the fuse panel on my 2008 Ranger. I had to replace it with a longer piece of wire. I used the radio fuse location to install the fuse tap. It worked fine when finished. Now the brake lights only function when the ignition is on. 476372
Works perfectly. I towed this car 10000 miles last year. Never had an issue. 476248
Your web site was very helpful, the item's received were exactly what I needed and expected, fast shipping. 458787
This product solved my problem only wished I would have known when I installed the wiring for my supplemental brake system. I had do go back and rewire it into the brake lite switch. The video on the 2016 wrangler was very helpful to look and compare especially at the fuse box. Thanks etrailer 454694
One thing I love about etrailer.com are the vehicle specific installation videos. I don't know how many they have but I have a 2006 Jeep Liberty and for everything I've purchased to set it up for towing behind my motorhome there's been an installation video. The same goes for the Roadmaster Brake-Lite Relay for Towed Vehicles. I'm jealous because the guys in the video make it look so simple. For me I've got a few aches and pains from working under the dash. I think the installation video was more informative than the printed instructions. As far as installing the brake light relay it was pretty straightforward thanks to the video. I did notice that some of the parts in my kit were slightly different from the ones in the video but I was able to figure it out. Once installed I tested the relay like was done in the video, by hooking it to my truck. The relay works as advertised and should solve my problem. The real test will come when I tow my Jeep Liberty behind my motorhome but I expect the results will be the same. 449564
Product was fine but isnt needed on a 2017 Equinox. 445737
Works great. 437090
Works as advertised. I have power coming from my bus for a portable brake system. This way I don't ruin the battery down. Since my Hummer H3 brake lights come on even with the key off, this allows the blinkers to work. Without it when my portable brake system depresses the brake pedal, it would override the blinkers. I energize this relay wth the power I feed to the brake system to open the brake pedal line in the car. Works exactly as expected. I installed and save a lot of money over other methods. 425124
Perfect fir on my 2017 jeep rubicon rec on 414331
All of the products I've bought from etrailer has been wonderful. There prices are inline and the how to videos are the best. Great company, great service and I will continue to buy from them. Tom S. 403583
Love the products, everything is working great. We are on the road now in Montana. Having the Jeep with us is wonderful.
Tom S - 07/10/2018I am very happy with my new tow bar system. Lisa and her team at etrailer.com did a great job for me. I recommend then highly. 403554
I am still very happy with the tow equipment and etrailer. Thank you.
Mike C - 07/10/2018Ask the Experts about this Roadmaster Tow Bar Braking Systems
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