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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:
95% were satisfied with this product
5% of customers were not satisfied
Ratings & Reviews
Glenn
1/29/2025
Excellent wiring system. Just make sure you have all your connections in place and set before sealing the back of the main plug as you will not get back in there again. The wiring coil line connecting the RV to the Jeep is very tight but has proven itself over thousands of miles. I can recommend it.
Jameson C.
1/29/2025
Nick S.
9/8/2025
I am sorry to hear about the adapter cord not keeping a good connection. I recommend inspecting each of the prongs in the adapter cord as well as the plugs on the RV and vehicle. One of the prongs could be bent or damaged causing that cord to not hold a steady connection when towing. Let me know if you notice any damaged prongs and we can figure out how to get that resolved for you.
Jim
2/28/2026
Still going strong. No problems at all. A very dependable air brake system.
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Jay
1/7/2025
What can I say other then it works every time and it is easy to hook and unhook