Roadmaster Brake-Lite Relay Kit for Towed Vehicles
(501 reviews)
Price: $39.05
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Roadmaster Brake-Lite Relay Kit for Towed Vehicles
Item # RM-88400
Retail:$45.90
Our Price: $39.05
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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.
- Remove the blue wire from the kit. This wire is not needed for normally open applications.
- Locate the brake-light-switch wire in your towed car.
- Remove the brake light fuse.
- Cut the brake light wire a few inches away from the "cold" side of the brake light switch.
- 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.
- Connect the black wire of the relay to the brake light wire near the brake light itself using the included blue butt connector.
- 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.
- Using the attached blue butt connector, connect the red wire from the brake relay to the wire from the fuse tap.
- Ground the white wire to your towed vehicle's frame.
- 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.
- 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.
- Locate the brake-light-switch wire in your towed car.
- Remove the brake light fuse.
- Cut the brake light wire a few inches away from the "cold" side of the brake light switch.
- 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.
- Connect the black wire of the relay to the brake light wire near the brake light itself using the included blue butt connector.
- 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.
- 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.
- 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).
- Ground the white wire to your towed car's frame.
- Secure the relay with the included wire ties.
88400 Road Master Brake Light Relay
Installation Details
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Customer Reviews
Roadmaster Brake-Lite Relay Kit for Towed Vehicles - RM-88400
Average Customer Rating: 4.8 out of 5 stars (500 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.by: Abraham11/15/2023
The proportional breaking never worked right and on our last trip the system kept cutting out until it quit working all together. I was in the southern US and had to drive back to Canada without the aid of the breaking system. i tried to check it out and fix it but was unable to get continuous power to the brake buddy.
by: Richard10/24/2017
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.
by: Dean 10/18/2023
The brake light relay kit has worked well for a full year now!
Simple installation, perfect compatibility with other braking components.
Would highly recommend this product!
by: Gary11/09/2023
Installing on 2020 Jeep Trailhawk :
Pic #0557 : Roadmaster Base Plate Kit , Demco Supplemental Braking System , Diode Wiring Kit , Demco Battery Charge Wire Kit
Pic # 0548 ,0551 , 0559 Had to adjust the bracket plate to line up with the upper bolt holes
Pic #6028 finished install , mounted the operating unit to the top fuse box cover using automotive Velcro . Air cylinder , controller and LED light installed . Aside from the base plate bracket not lining up with the upper bolt holes I would give it 4 stars . My son in law is a master at solving mechanical issues .
by: Roger 11/09/2023
Exactly as described - all parts included to install the brake light relay.
by: Doug 08/11/2023
I used this on a 1988 Toyota Land Cruiser, so I could flat tow it behind an Motorhome. Easy to install!
by: Jeffrey12/22/2021
I have successfully completed the installation of the following items that I purchased from etrailer:
> Nighthawk RM-676 tow bar
> RM-524458-5 base plate
> DEMCO Stay in play DM86VR
> RM-152 diode wiring kit
> RM-156-25 charge wire kit
> RM-88400 brake switch relay kit
I work slow but methodically. I had no issues other than the high degree of difficulty for a 68 y/o man working alone. This project exceeds the abilities of someone NOT mechanically inclined. There is also the need for some specialty tools. I found that feeding the wiring through the dash, firewall, and underbody was more difficult than installing the front baseplate. Overall, I am satisfied with the function of this installation. I am glad I did it myself rather than having it done.
Tow vehicle: 2021 Entegra Emblem 36U
Towed vehicle: 2018 Ford Fusion Platinum Energi
Jeffrey
11/19/2022
The performance of this tow bar and associated hardware has been outstanding! Service and warranty follow up service from Roadmaster has also been outstanding! I am very satisfied with my purchase.
by: Donald05/26/2023
We tow a 2022 Ford Escape behind our Winnebago motorhome. This wiring kit did the job for us. Everything working great!
by: Dale09/27/2023
Works as advertised. Install instructions easy to follow.
by: Michael 08/06/2023
It was a little tricky to install but easy to adjust the switch setting for precise response to brake pedal movements. Instructions were easy to follow follow and accurate.
by: Craig03/31/2023
This system has been great. I use it to tow my Jeep behind a Ford Transit van and it has worked flawlessly for the last year. The only thing I have had to replace was the plug in adapter in the front ($40 part), that wore from some tough winter weather we went through. It is easy to use. it takes us less than 5 minutes to completely set up our tow vehicle.
by: Charlie 07/05/2023
Good kit. Includes everything you need. Good instructions. Continues to work perfectly after one year and many towing sessions.
by: Andrew 08/08/2023
Needed this for my F150 flat towing
by: Oriel12/02/2023
Great service an excellent product the guy that delt with me was on point .thanks for you follow up..
by: Hans04/13/2022
Fairly easy to install, especially with the aid of the etrailer videos, and it works great on my 2016 Wrangler
Hans
4/17/2023
After a year it still works great.
by: Richard 07/13/2023
Works great, but you need to be a contortionist to get behind the brake pedal to access the wires to cut this in.
by: Jeanette 11/29/2023
Our tow kit has been exceptional. No problems. Easy to attach. No complaints.
by: Michael09/07/2022
Did not use. I ordered the wrong system and returned.
Michael
9/9/2023
Dont know. I returned it.
Mike L.
11/1/2023
@Michael Why did that happen? What was the problem?
by: Troy05/21/2023
Installer did not get this installed correctly. Figuring out if it was needed or not was an ordeal. Lost of conflicting information in the product description and on website. It was needed and doesn’t work correctly, but I don’t think it’s the products fault. Make sure you get a competent installer.
by: Garry07/12/2023
Excellent product. Delivered on time, all my questions were answered. Great company I would recommend to anyone.
by: Lee02/11/2021
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.
by: Kim12/28/2022
Thank you for including the fuse.
Oh my! Testing for that brake light. I finally found a tool where one person could handle testing and then pressing on the brake pedal a normal probe DC tester was impossible for me to use. Be ready to do some under the dash yoga poses!
The parts for this don't quite match the video, once again look at the diagram to verify. But once installed it worked for the tests (don't forget to ground), now to get rolling.
When ordering this spend the extra money on a Hook Probe Circuit Tester Item # PTW2993
by: Kenneth 06/27/2022
Easy to install. Easy to remove. Tows great. No problems at all. Pulling with our Thor Palozzo.
Kenneth
6/28/2023
No problem
by: Denny11/02/2022
Outstanding product and even better customer service! Two backyard mechanics installed baseplate and braking system with just one call to confirm proper wire connection. Total package works great.
by: Richard01/19/2023
I haven't installed this & won't get to it till the end of February. Do you have a video outlining this installation?
Brooke M.
1/23/2023
We do! At the top of the product page, below the pictures, you will see the multiple install videos we have posted to help our neighbors, like you!
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See what our Experts say about this Roadmaster Tow Bar Braking Systems
- 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...
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- Installing the Brake Light Relay on a Key-Start 2017 Jeep Cherokee TrailhawkI did some checking and the brake light relay # RM-88400 is not required to flat tow the 2017 Jeep Cherokee though there may be circumstances where it is needed. I have included a link to the only video we have showing installation of the relay on a 2017 Jeep Cherokee for you but it is a push-button start so not all of it will apply to you. I have also included our picture showing how it gets wired in the normally open configuration. The explanation of that diagram is as follows: 1) Remove...
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- What is the Function of the Extra Red Wire that Comes with the Brake Light Relay RM-88400The extra loose red wire that comes with the brake light relay # RM-88400 attaches to the hot side of any fuse that has power only when the ignition is on. So the red wire from the relay will go into the yellow in line fuse. One end of that extra red wire will go in the other end of the in line fuse. Then the opposite end of the extra red wire will make the connection to the fuse panel using the included fuse tap and spade connector. The monitor light and wire that tells you that the brake...
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- Is the # RM-88400 Brake-Lite Relay Needed on a 2002 Jeep Liberty When Using Supplemental BrakingWhen determining if you will need the Roadmaster Brake-Lite Relay Kit, # RM-88400, on your 2011 Jeep Liberty, there a few factors that must be considered. If you plan to use a supplemental braking system that depresses the brake pedal, if your towed vehicle's brake light and turn signal light are on the same bulb, and if you brake lights illuminate when pressing the brake pedal when the ignition is off, then you will need to install the # RM-88400 brake relay. The relay prevents your...
view full answer... - Troubleshooting Roadmaster Brake-Lite Relay Kit for Towed Vehicles # RM-88400 Light IssuesYour brakes lights should be illuminating when the brake pedal is depressed when using the Roadmaster Brake-Lite Relay Kit for Towed Vehicles # RM-88400. When using the relay kit, your vehicle's lights should mimic those of your RV. I would check the wiring to ensure the Relay Kit was wired correctly, I am attaching a wiring diagram for you to see how it should be connected.
view full answer...
- Do I Need A Brake Light Relay For A 2023 Ford Ranger?Yes, you will need a brake light relay for your 2023 Ford Ranger. For that we recommend the Roadmaster Brake-Lite Relay Kit # RM-88400. This is going to be required to prevent the towed vehicle's brake signal from overriding the turn signal from the RV when applying the brakes during a turn. I have linked our install video for a 2022 Ford Ranger Below.
view full answer... - How To Wire In The Roadmaster Brake-Lite Relay Kit In A 2016 Jeep Wrangler UnlimitedAuto-start on the key fob will not change the the installation of the Roadmaster Brake-Lite Relay Kit # RM-88400. If you have to physically insert a key into the ignition to operate the vehicle you'll need to complete the installation using the 'Normally Open' wiring method. If you have a push-button ignition and do not need to use your physical key to operate the vehicle then you would follow the 'Normally Closed' wiring method.
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- Wiring a Roadmaster Brake Lite Relay Kit on a 2010 Honda FitYes, you will need to utilize the black wire on the Roadmaster Brake-Lite relay kit # RM-88400. You will need to find that green/silver wire at the brake switch (above your brake pedal), cut it about 6 inches away from the switch. The end going to the brake switch you will attach the relay green wire. And the end going out to the brake lights you will attach the relay black wire. See the diagram I included. The relay kit # RM-88400 will prevent your 2010 Honda Fit brake signal from overriding...
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- Do I Need a Brake Light Relay for Flat-Towing a 2022 Jeep Wrangler?There are a few questions to consider in order to determine whether your 2022 Jeep Wrangler will require a brake light relay like part # RM-88400. I included this question tree to guide you through those 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...
view full answer... - Troubleshooting Roadmaster Brake-Lite Relay Kit on 2015 Jeep CherokeeI 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 push...
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- Can Connection of Brake Lite Relay to Stoplight Switch be At Brake PedalYou can attach the Brake Lite Relay part # RM-88400 to the stoplight switch at the pedal like you mentioned.
view full answer... - Installation Video of Roadmaster Brake-Lit Relay in 2015 Jeep Wrangler UnlimitedMost likely you will not need a brake light relay for your 2015 Jeep Wrangler Unlimited. I recommend wiring the Wrangler first and checking to see if you need a brake light relay before installing it. You will want to connect the Jeep's wiring to the motor home's, put the Jeep in tow mode, turn on the motor home's blinker, and then have a helper step on the Jeep's brake. If the turn signal continues to blink on the Jeep, you will not need a brake light relay. We have not installed the...
view full answer... - Brake-Lite Relay Kit For A 2021 Jeep Wrangler SportYes, The Roadmaster Brake-Lite Relay Kit for Towed Vehicles # RM-88400 will work with your wiring system to ensure that your towed vehicle's turn signal lights flash in tandem with your RV's lights. Using this relay will not interfere with your towed car's electrical system. It will activate automatically when RV running lights are turned on. I attached a review video link below.
view full answer... - Installation Of Brake-Lite Relay On 2017 Jeep Wrangler UnlimitedThe Roadmaster Brake-Lite Relay Kit for Towed Vehicles, part # RM-88400 comes with an inline fuse that is attached to the red wire from the relay to the fuse panel under the hood on your 2017 Wrangler Unlimited. I have attached a link to an installation video for this relay that shows in great detail how to install the relay. At about the 11 minute 30-second mark it shows what fuse in the fuse panel on your Jeep is used and also how to attach the inline fuse for the relay. If you have...
view full answer... - Brake Light Relay Recommendation for 2008 Jeep Grand Cherokee Using Braking System Presses PedalSince the braking system you plan to install on your 2008 Jeep Grand Cherokee applies the brakes of the vehicle and the brake lights of your vehicle come on when you press the brake pedal you will need the brake light relay part # RM-88400 which is designed to allow the blinkers to still work when the brakes are applied.
view full answer... - Can The Roadmaster Brake-Lite Relay Kit Be Used In A 1995 Jeep Wrangler The Roadmaster Brake-Lite Relay Kit for Towed Vehicles # RM-88400 is a universal fit item so you would be able to use it in a 1995 Jeep Wrangler.
view full answer... - Amperage of Fuse on Roadmaster Brake-Lite RelayThe fuse tap uses the provided 10 amp fuse with the Roadmaster Brake-Lite Relay Kit for Towed Vehicles # RM-88400.
view full answer... - Recommended Brake Light Relay Kit For 2015 Jeep Cherokee Trailhawk Being Flat-TowedI called my contact at Roadmaster about your Cherokee Trailhawk. They told me that if you are using a supplemental brake system that physically pushes on the brake pedal in your Jeep, it will drain the battery. We do have a solution for you. You can install a brake light relay like part # RM-88400. This installs on the stop light switch wire that goes from the stop light switch at the top of your brake pedal to the lights on your Jeep. When the motorhome is connected to the Jeep this...
view full answer... - Wiring FAQ about Roadmaster Brake-Lite Relay Kit As far as your question, you are correct, the Roadmaster Brake-Lite Relay Kit for Towed Vehicles # RM-88400 relay on a push button start is just looking for a 12v signal. My contact from the manufacturer Roadmaster says, they use the tail light feed since it is already existing and customer does not have extra wiring to connect and it is easy to make part of their hook up routine. If you are going to supply with a different source, you just need to ensure that you supply that power every...
view full answer... - Signal Lights not Working on Towed 2012 Honda CR-V when Brake Light is OnWe have exactly what you will need to resolve the brake and signal light issues you are experiencing when towing your 2012 Honda CR-V. You will just need to install the Roadmaster Brake-Lite Relay Kit # RM-88400. This is needed on your vehicle to keep the CR-V's brake signal from overriding the turn signal sent by the RV. This will not interfere with your vehicle's electrical system and will automatically activate when the RV running lights are turned on. I have attached an installation...
view full answer... - When Installing Brake Light Relay on a 2013 Ford Edge Should it Be Normally Open or ClosedI looked through an online copy of the owners manual for the 2013 Ford Edge Limited and the #59 fuse looks to me like the only one you would need to pull. If the vehicle still starts then you would need to go with the normally open instructions for brake light relay # RM-88400. I have included a picture showing how it is set up normally open.
view full answer...
- Where Does Red wire of Roadmaster Brake Lite Relay RunThe red wire of the Roadmaster Brake Lite Relay kit part # RM-88400 runs to a circuit on the vehicle that only sees voltage when the key is in the on position. I attached a diagram for more info as well.
view full answer...
- Brake Lights Not Working After Install of RM-88400If you have a flat tow wiring kit with diodes, then you need the Roadmaster # RM-88400 Brake Light Relay Kit. It is normal behavior for those lights not to work when the wiring kit is active. We want the towing vehicle (through the wiring kit) to control those lights.
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Richard
10/24/2018
Working great with no problems.