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Smart diodes are our favorite option for getting brake and turn signals on your towed car. They are really well-made and reliable, plus pretty easy to install. This complete kit includes everything you need for multiplex LED tail lights.
Features:
Specs:
Notes:
"Don't be intimidated by diodes: if you can strip and crimp wire, this installation will be no problem."
A variable voltage tail light (also known as multiplex) uses the same wire for both the brake light and the tail light, sending a 12-volt signal to the brake light and a 9-volt signal to the tail light. This works fine when you're driving, but when you are flat towing, the RV will send a 12-volt signal to both the brake light and tail light, making them the same level of brightness and impossible to distinguish from each other. The drivers behind you won't be able to tell the difference between your tail lights and your brake lights, which is a huge safety issue.
These smart diodes solve that problem by simply converting the signal from the RV to the lower voltage needed for your car's tail lights. They install permanently, but don't worry; everything will work as normal when you're not flat towing.
This kit is designed to work with LED lights only, so if you have incandescent variable voltage lights, you'll need kit RM26FR (sold separately) instead.
If the engine is off and your car's brake lights illuminate when you press the brake pedal, you need to install a brake light relay (RM-88400 - sold separately) with this kit. Without a relay, your car's brake signal will override the turn signal sent by the RV when you are slowing down to make a turn, creating a potentially dangerous situation. Other drivers will see that you're slowing down, but not that you're making a turn. With a brake light relay, you can signal both and travel safely.
A combined lighting system, or 2-wire system, uses the same light bulb to signal both braking and turning. (In other words, the car signals a turn by flashing the brake light.)
A separate lighting system, or 3-wire system, has the brake signal and the turn signal light up independently of each other. Typically, the turn signal is amber.
If your motorhome has a separate lighting system, add a tail light wiring converter (RM-732 - sold separately) to keep your setup functioning properly.
Customer Satisfaction Score:
98% were satisfied with this product
2% of customers were not satisfied
Ratings & Reviews
Great company with excellent service.
You guys are excellent. What great service and follow up. I also know you'll be there to answer questions as I do the install
Required. Installed by local garage.
Awesome company & awesome customer serv ice
No issues with my wiring kit.
4 conductor wire was to short. I did not waste any wire and it was 6’ to short.
Jenny N.
7/3/2023
It is unusual that the wiring would come up short. Would you be able to send a picture? How long was the wiring that you received?
Customer Service was excellent - 5 STARS. The smart diodes are another matter. They are very poorly made. Connections had to be taped together in for them to stay together. They are inferior, cheaply made and will not crimp. Your instructional video was very good.
Product works but is a bit flimsy. Also, the connectors are an unusual size, 3/8 vs 1/4 inch, making it harder to purchase replacements if needed.
The instruction from etrailer did not match the written instructions from Roadmaster. There were a couple of issue that took me the better part of a day to work through. The install was on a 2024 Jeep 4XE (4 door) that had LED tail lights.
The challenge was which of the jeep tail light (running lights) feeds to splice the diode's into to assure the system worked. The etrailer video said to use the brake feed, the Roadmaster said to use the tail light feed. If you use the brake feed, then you will have a conflict with the Jeep brake pedal on the tow vehicle, as this will override the blinkers. There is a work around (another product and another ~$[XX] that could over come this).
The problem with the tail light feed is there are 3 of the 12 pins that have 12V power when the tail lights are turned on. After calling roadmaster, they pointed me torwards the right direction, but it was still trial and error. I finally found a Jeep wiring diagram and used PIN 4 to feed the diodes.
Then the power out of the diode, to feed the taillights caused the LEDs to be extremely dim, only about 5 volts were being fed out to the Jeep Tail lights from the diode side. Did not have any issue with the blinkers or the brake lights (from the motorhome), just with the running lights.
Recommend etrailer & Roadmaster determine which approach to use and make the kit so an installer does not need to loose a full day of trial and error.
Brooke M.
5/5/2025
Hey Clark! I'm sorry it felt like you were having to run around to find what you needed. It sounds like you may have the Road Master braking system and depending on what vehicle you have, you may be need part # RM-88400. If you go to the product page and scroll down a little, you'll see a flow chart of "yes" "no" questions that help determine if you need this part for your set up.
EASY TO INSTALL
Exactly what I needed and quick shipping
Works very well
I ran this wiring thru the frame and was the easiest way to the back. The unit I had was a unit for led and parking assist. It works great. The wiring in the back is covered with a plastic sheath and need to cut it back some . So a little different but can be done.
This product was exactly as described, and worked well to hook up the taillights in our towed vehicle. Thanks
William
4/28/2025
This product has been working perfectly since installing about 1 year ago, Thanks!
Just got it and I’ll update once I install it
John
3/9/2026
Perfect! Easy install with out any problems
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James
11/22/2025
Great!, exactly as expected with no issues. The videos etrailer supply are very helpful!