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Roadmaster Stop Light Switch Kit
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Roadmaster

Roadmaster Stop Light Switch Kit

Part Number: RM42MR
In Stock
$43.99
Retail:$64.09
You Save: 31%
Flat Tow Brake System
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etrailer Installation
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Avoid damage to your vehicle by ensuring that your supplemental braking system is properly positioned and working effectively. Kit activates your RV monitoring system to alert you when the brakes of your towed car are being applied. 1-800-940-8924 to order Roadmaster flat tow brake system part number RM42MR or order online at etrailer.com. Free expert support on all Roadmaster products. Great prices and Fastest Shipping for Roadmaster Stop Light Switch Kit. Flat Tow Brake System reviews from real customers.
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Roadmaster Flat Tow Brake System - RM42MR

Highlights

  • Protects Your Towed Vehicle: Lets your RV alert you when the toad’s brake pedal is pressed so you can catch issues before damage occurs
  • Confirms Brake System Is Working: Signals when your supplemental braking system actually applies the pedal, not just when air pressure changes
  • Prevents Costly Brake Drag: Helps avoid continuous pedal pressure that can wear tires or overheat brakes
  • Works When Ignition Is Off: Gives a reliable brake signal even if your vehicle doesn’t have a “tow” key position
  • Easy Wired Connection: Installs directly into your vehicle’s fuse box for a steady 12-volt current
Made in USA

Features to know about

Always Know When Your Brakes Are Working: Direct Pedal Signal to Your RV

When you’re towing, you need to be sure your supplemental braking system is doing its job. The Roadmaster Stop Light Switch Kit sends a direct signal from your towed car’s brake pedal to your RV’s monitoring system, activating the alert any time the pedal is actually pressed. That means you’re seeing what’s really happening—not just whether the system is trying to brake. It gives you peace of mind knowing your brakes are reacting exactly when they should.

Protects Against Costly Brake Damage: Confirms Proper Braking Operation

Improperly installed or malfunctioning braking systems can cause your towed car’s brakes to drag or fail to release, leading to tire wear or brake damage. This kit ensures everything is positioned and functioning correctly by verifying when the pedal is depressed. With that feedback, you’ll know right away if something’s off before it causes expensive damage.

Reliable Power Connection: 12-Volt Wiring for Steady Performance

The Stop Light Switch Kit wires directly into the towed car’s fuse box for a constant 12-volt current. This steady connection keeps your monitoring system accurate and responsive. It’s a dependable solution for setups that don’t have a “tow” position in the ignition, so your brake alerts stay active whenever you’re on the road.

Simple Confidence Every Trip: Custom-Fit Design

Built specifically for your vehicle, this Roadmaster kit integrates neatly into your setup. Once installed, it works in the background every time you tow—no extra steps or adjustments needed. It’s a small addition that makes every trip feel a lot more secure.

Specs

Electrical

  • Voltage: 12 Volts

Application

  • Fit: Custom fit for your vehicle

What You Need to Flat Tow

Flat towing can be a much more convenient way to take your car RVing with you than using a trailer or a tow dolly. It'll save you storage space both at home and at the campsite, and it takes less time and hassle to hook up.


To flat tow your vehicle, there are 5 basic components you're going to need: a tow bar, a base plate kit, a safety cable set, tow bar wiring, and a flat tow braking system.


For the RV Between the RV and Towed Car For the Towed Car
Hitch Tow bar Base plate
Wiring plug Safety cables Braking system
Wiring adapter cord Wiring kit/diodes

The custom-fit base plate installs on the frame of your toad so you can connect the car to your RV with a tow bar. Hook up safety cables between the vehicles to ensure that the toad does not separate from the motorhome if the tow bar becomes detached. Tow bar wiring syncs your vehicle's signal lights with your motorhome's tail lights, as required by law in most states. Finally, the flat tow braking system - also required in most states - activates the brakes in the toad when you hit the brakes in the RV, making for smoother, safer braking, and preventing wear on your motorhome.

751510 Road Master Stop Light Switch Kit

Installation Details RM42MR Installation instructions

This Product Fits The Following Vehicles




Customer Satisfaction Score:

Ratings & Reviews

4.7

707 reviews
Review sort icon
Avoid damage to your vehicle by ensuring that your supplemental braking system is properly positioned and working effectively. Kit activates your RV monitoring system to alert you when the brakes of your towed car are being applied.

by:

Ive installed the ble ox base plate bx2654 and the remote battery disconnect #766. Installation was easy great instructions to follow. Also installed 12 volt outlet kit #9332. I'm installing led bulb and socket kit 152-led. Great so far.



by:

This is the second switch I’ve bought. The fuse holder could be designed a little better. Perhaps with the wire out the top rather than the side.



by:

Great product installed very easily. I also used this switch to install a Brake Controller. By using this I did not have to tap into the Wrangler electrical system for the Bake Controller.



by:

Did not use



by:

The instructions are a little difficult to follow but it was easy to install



by:

Easy installation. I had an issue getting the kit ordered, but the customer service agent was phenomenal in her assistance getting it resolved.



by:

Mount was good and directions easy to f ollow.



by:

Installed on a 2023 Equinox LT (AWD). I believe there may have been a change to the Equinox brake pedal assembly from prior years. Because of this, I was not able to get the switch located properly with the bracket that is included in the kit. I fashioned my own mounting plate from a piece of diamondplate which I bolted to the brake lever bracketry. This works great and is rock solid.



by:

etrailer’s installation video was very helpful. However, the mounting bracket holes on either end seem to be the same size (the video and instructions state that the switch fits into only one end but for me it fit into both). Consequently, it is not clear which side of the bracket to use for the switch vs the vehicle stud. One other installation hint, perhaps unique to the Wrangler Rubicon or Wranglers with upgraded audio/Uconnect, there is an electronic module (3”x4”), mounted to the dash framework behind the lower dash panel, that must be dismounted in order to allow access to the bracket mounting location (see photo).



by:

It works as designed. Tricky for this old fat guy to work under the jeep dash but eventually got it installed and adjusted.



by:

Was disappointed that your site said this was the part I needed so I ordered it. Then realized it was not correct part. Called next day to cancel and Oder correct part. I was told I could not cancel it and would have to pay to ship it back. The correct part which was ordered second came 2 days before first part. To get a refund I still had to pay to ship it back. Other than this trailer has been good to work with and quality parts.



by:

Thank you, order arrived as promised, and install was easy and fit my 2025 Jeep Grand Cherokee Overland perfect to operate my brake light on my Motorhome dash.



by:

Easy installation. Fit perfectly in my 2014 Grand Cherokee.



by:

Ill give it 3 stars because I had to shim the bracket to make the plunger line up with the brake arm. But it works well so far.



by:

It is my opinion that the universal brake light switch is the easy way to go. Hardest part doing the DIY way is the place you are working in. I.have a few sore spots trying to get underneath the steering wheel. The benefit is you have instant info that the switch works. A light comes on when you push the break pedal



by:

Works great fairly easy install. It has been in use for the last 8 month's with no issues. Here may be some helpful hints that I found when installing. Use 10-12" long extension for 13mm nut (left side of opening panel that was removed). Install bracket. Adjust plunger & backing nut by feel. Remove bracket. Install switch with ring washer & nut. Crimp red & green wires on switch wires. Reinstall bracket under dash.



by:

Roadmaster products are great, very pleased with the superb instructions. Very difficult to mount the pulley for the invisibrake in my Ford Maverick. Trying to drill stainless steel behind the brake pedal was near impossible. Could a bracket for the pulley be mounted on the same studs as the Stop Light Switch?



by:

I have a ‘23 Bronco with the Lux package. The Bronco had a factory brake switch in the spot this thing would go. Advice was unclear whether I could use a factory wire to install my brake controller. I went with the wire that lit the test light when brakes were pressed (key on). I think it was violet with a stripe at the plug for a factory Brake controller. I don’t have the factory tow package. Seems to work but not yet tested with a trailer. Only 3 stars because of the uncertainty. I’ll use this switch on a different project.



by:

Product works great...But was shorted the female connector to terminal 1...Cost over 5 dollars at Auto Zone.As no one sells just one.....Its in the picture...Not in my parts bag...But a perfect fit on the brake switch mount .Three stars only because I had to go buy a connector to complete the job.



by:

One year later and I haven't had to touch this system even once. It just works, all the time, every time. Very happy with this kit. Works perfectly in my 2019 Toad (Jeep Cherokee).



by:

I couldn’t use the towed vehicle’s brake light circuit on the last two pickups I’ve set up. On the truck before this I robbed a little refrigerator switch that turns on the light when you open the door and rigged up my own. Alas, that wouldn’t work on this newest GMC Canyon. Then I found this device. Wow, what a quick and easy installation. It works perfectly.

I do have a suggestion for ETrailer. Show the actual switch dimensions in your listing. Though the actual switch is quite small, I was worried I wouldn’t be able to make it fit. With nothing but pictures and nothing for scale, it was a concern.



by:

I installed the item in my 2024 Bronco to support braking indication in the motorhome while being towed, since Ford does not include one these days. As far as I can tell, this is the only commercially available kit to avoid cobbling up your own design. It is tedious to install mechanically and, especially tedious to adjust transverse mount position and depth of travel. The button on the switch is too small, requiring very precise alignment to the brake pedal arm (approx 1/4" wide) in the transverse direction from the switch movement. There is no screw type adjustment in that direction so bracket bending/and or bracket mounting spacers is required. I am also afraid the switch button being small and made of some type of poly, it will slip sideways, deform, or wear with even the slightest offset and begin to push the bracket aside. However, it has worked in a few thousand miles of towing behind a motorhome so far. I will keep an eye on this and test function whenever hooking up to tow (a normal practice anyway). I kept thinking it would be easier to use a long lever low force microswitch instead of a tiny soft-tipped, rather hard spring or drag, pushbutton, which would require its own mounting design. Maybe a small highly adjustable ball clamp mount work with a microswitch as well. But I must resist my engineering background tendencies in exchange for getting the job done! Sorry for the quality of the photos. It is in a difficult place for phone camera.



by:

Thanks everyone at etrailer for your help and quick response and shipping! My project turned out really great as you can see in the pictures I have included. The plug for the removable holders I 3D printed. Thanks Fred



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by:

Great product


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See what our Experts say about this Roadmaster Flat Tow Brake System

  • Complete Flat Tow Set Up For 2024 Ford F150 4x4 Hybrid
    Hello Vance. Wow, that is a nice truck to pull behind your motorhome! Here are all the parts I recommend for flat towing your 2024 Ford F150 4x4 Hybrid: -Base Plate Kit: Demco Tabless Base Plate Kit - Removable Arms # DM56MV -Tow Bars: Demco Dominator Non-Binding Tow Bar - RV Mount - 2" Hitch - 7,500 lbs # DM9511008 -Wiring Kit: For LED tail lights- Roadmaster Smart Diode 7-Wire to 6-Wire Wiring Kit for Variable Voltage LED Tail Lights # RM38FR. For Incandescent tail lights- Roadmaster...
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  • Availability of Hopkins Brake Light Relay for 2025 Ford F-150
    Hey Jay! Hopkins is for sale right now since they're part of First Brands which went bankrupt. We don't actually know when the Hopkins Custom Tail Light Wiring Kit # HM77VR will be back, and we don't have that relay either. Even if we did have it, I highly recommend using the Roadmaster 4-Diode Universal Wiring Kit for Towed Vehicles # RM-15267 instead. Roadmaster has the most reliable wiring which is exactly what you want when you're flat towing. You will also want a 6-way, which this...
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  • Trouble Finding Brake Light Wire on a 2025 Ford F-150
    Hey Dennis, thanks for reaching out! According to the Roadmaster fitguide you're going to need a brake light switch as well since they weren't able to locate the color of the OEM brake light circuit wire. You'll use part # RM42MR if you have an adjustable brake pedal, or part # RM89ZR if you don't have an adjustable brake pedal. Once the brake light switch kit is in place, you'll have the signal you need to install the Brake-Lite Relay Kit # RM-88400. Are you installing all of your flat...
    view full answer...
  • Location of Cold Side of Stop Light Switch for Brake Controller Installation on 2022 Ford F-150
    It looks like the OEM brake light switch is unusable on the 2022 Ford F-150. To complete the installation you will need to add the RoadMaster Stop Light Switch Kit # RM89ZR if you do NOT have an adjustable brake pedal or # RM42MR if you DO have an adjustable brake pedal. The red wire on your # RED52VR will connect to this to complete the installation.
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  • Location of Brake Light Switch on 2024 Ford F-150 Raptor
    Hi Terry; I'm not sure what the exact location of the brake light switch is but we do know that it is unusable on the 2024 F-150 Raptor. What you will need to do is install the Roadmaster Stop Light Switch Kit # RM42MR. If you don't already have a wiring kit so you can use your tail lights while flat towing you need the Roadmaster Diode 7-Wire to 6-Wire Flexo-Coil Wiring Kit # RM-15267. You will also want a charge line kit # RM-156-25. I see you also looked at some supplemental braking...
    view full answer...
  • Correct Roadmaster BrakeMaster Seat Adapter for a 2024 Ford F-150
    Hey Steve! The correct seat adapter for your 2024 Ford F-150 is the Roadmaster item # RM-88316, you were looking at. This is designed for the Roadmaster BrakeMaster item # RM-9160-900002 and item # RM-9060-900002. You're also going to need a stop light switch. There's two options depending on what brake pedals you have. I have listed them below: Adjustable Pedals - Roadmaster Stop Light Switch Kit item # RM42MR Non-Adjustable Pedals - RoadMaster Stop Light Switch Kit item # RM89ZR
    view full answer...
  • Location of Brake Light Switch on 2023 Ford F-150 Installing Roadmaster InvisiBrake
    Hey Paul! The OEM switch on your 2023 F-150 is unusable. You will need to add a RoadMaster Stop Light Switch Kit to complete the installation of your InvisiBrake # RM-8700. You can choose from the following based on your configuration: -Non-Hybrid Model With Non-Adjustable Brake Pedals use # RM89ZR -Non-Hybrid Model With Adjustable Brake Pedals use # RM42MR -Hybrid Model use # RM-751000 What motorhome are you towing with and where are you headed once you get your F-150 set up?
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  • Steps To Find Cold Side Brake Light Switch Wire On 2023 Ford F-150 When Installing Brake Controller
    We haven't had a chance to install a brake controller in a 2023 Ford F-150 yet (3/27/2023), so I can't tell you the wire color but I can tell you how to figure out which one you need to hook to. You'll need to use a circuit tester like # PTW2993 and with the truck on but not running, press the brake pedal and test the wires going to the brake switch (this will be a plastic looking thing on the brake pedal arm). You're looking for one that only has power when the pedal is pressed. If you...
    view full answer...
  • Will the Curt Custom Base Plate Kit C57NQ Fit a 2024 Ford F-150 Tremor?
    It sure will Mark! The Curt Custom Base Plate Kit item # C57NQ will indeed work with the Tremor models of the 2024 Ford F-150. I linked the installation instructions below. There's an entire section starting on page 9 that details the specific steps you'll need to follow relating to the skid plate. Here are the rest of the parts you'll need to flat tow your 2024 Ford F-150 Tremor: Tow Bar and Safety Cables - Curt Rambler item # C25DQ Wiring Harness - Roadmaster Smart Diode 7-Wire to...
    view full answer...

Do you have a question about this Flat Tow Brake System?


Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Jeff D
Installed by:
Jeff D
Employee Ryan G
Installed by:
Ryan G
Employee Joshua S
Video Edited:
Joshua S
Employee Wilson B
Updated by:
Wilson B
Employee Amanda K
Written by:
Amanda K

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