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Roadmaster Single Park Light Diode

Roadmaster Single Park Light Diode

Part Number: RM-690
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Roadmaster Accessories and Parts - RM-690

  • Flat Tow Wiring Harness
  • Diodes
  • Roadmaster

Electrical damage can occur to the towed vehicle if its headlights are turned on while still connected to the motorhome. The Park Light Diode from Roadmaster will stop any interaction between the two park light systems, preventing electrical feedback and electrical damage.

  • Maximum load is 85 amps at 12 volts per diode
  • Qty: (1) Diode

690 Roadmaster Single Park Light Diode

Video of Roadmaster Single Park Light Diode

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Review of Roadmaster Tow Bar Wiring - Single Park Light Diode - RM-690

Hello everybody, this is Jeff at Today we're gonna take a look at this Roadmaster Single Park Light Diode. Now basically when you're flat towing your vehicle electrical damage can occur to the tow vehicle, if it's headlights are turned on while you're still connected to the motor home. So this park light diode here from Roadmaster will stop any interaction between the two park light systems preventing electrical feedback and electrical damage. Now they do recommend installing this diode directly behind the electrical socket on the front of your vehicle. However, it can be installed anywhere in line before the connection to the towed vehicle's wiring.

This does have nice aluminum heat sink which prevents overheating. On the back, you can see it has a nice self stick adhesive pad for secure mounting. Maximum load is 85 amps at 12 volts per diode and this part is for a quantity of one diode. But that should do it for the review on the Roadmaster Single Park Light Diode..

Customer Satisfaction Score:

Customer Reviews

Roadmaster Single Park Light Diode - RM-690

Average Customer Rating:  4.8 out of 5 stars   (99 Customer Reviews)


I didn't quite use this for the intended purpose. I was having trouble with the hazard lights backfeeding the brake controller and pulsing the trailer brakes on my 1988 Chevy 1 ton pickup. Broke out the wiring diagrams and turns out on the squarbodies, that's how they wired the brake lights. Installed this diode after the brake light switch and brake controller but before the hazard switch. Solved the problem. The diode seems to be built well. The fact that it has blade terminals on it makes the installation easy. Very happy so far.


It did exactly what I needed it to


My application is a little different. I had used a relay to feed battery voltage directly to the ignition coil on my 65 Corvair. The alternator warning light back fed from the battery causing the engine to keep running with the key off. I installed the diode in the line to the warning light. Problem solved. Great product. Easy to install and works as described.


Worked perfectly, just needed to buy 4 more!


Used this in conjunction with a 12V charge line from my Class A motorhome to the battery in my Jeep to provide charge to battery when towing and using BrakeBuddy. Prevents backflow discharge when stopped. Also put in fuse at front of coach and fuse at Jeep battery as protection for 12V system in case of chaffed wire or grounding.

Greg S.


Towed that Jeep to several places last year. Still works just like its supposed to.


Great product that works as it’s supposed to…


I bought 3 diodes for my 09 Saturn that was back feeding to my RV. This took care of the problem. Easy is it to install and peace of mind that I won't have a problem now . Had I known I didn't hade diodes on my wiring harness I would install them at the same time .but buyer beware on buying other people's products not for E trailer .



Its been one year now and a diodes are still doing their job


Very fast and easy transition. My order was delivered quickly and on delivered on time. This is my first purchase from etrailer, and I plan to buy from them again.
The product will be used in the 12 volt output of a Motorhome trailer connector to feed a tow vehicle. The diode is rated at 85 amps which covers any need I might have. The construction of the diode is first rate.



Product is still working fine without any problems


Works as described. I used it in the charge line from the motorhome to the towed vehicle battery (2012 CR-V, diode in from charge line, diode out to CR-V battery).

John F.


It still works as intended with no problems.


Product serves my application. Wanted to be sure that the break away emergency battery power on trailer brakes, when activated, would not back feed to my truck and damage factory brake controller.
Installed in 7 conductor cable between truck and trailer. Under test it works fine. Hope I never need it on the road. Recommend it for protection from back feed voltage. Could be used in any DC voltage system when the flow of current must be controlled or protected.


Pretty basic item here, it prevents current from going back and forth. And it does just that! Worked perfect for my situation on the living quarters gooseneck horse trailer. I had installed a new battery breakaway system that charges the battery when the trailer is plugged in to the truck. However in my case, when the trailer wasn't plugged into the truck, I was getting current back through the wiring harness from the house batteries that was charging the breakaway battery. Not good as over a short time period it would have drained the house batteries. This little item prevents that from happening. Thanks Guys!


Didn't know I needed this to wire my 7 pin connector for trailer brakes. My neighbor told me I would need it so I ordered it. It works great. I suggest you mention it when someone orders a 7 pin wiring harness for a newer car.




This has worked great on my boat keeping my trolling battery charged while fish. It keeps it topped off.


The road master diode worked perfect I used it as a battery isolater between my trailer winch battery and my trailer brake battery so when I would use the electric winch it doesn't drain my trailer brake battery with combination with a isolater switch so long u wire it correctly it works perfect.


This product works exactly as desired. The packaging is excellent, and it did the trick. I'd definitely recommend it to prevent backfeeding.

I'm very happy with etrailer, their selection of products, pricing, and their information. They truly differentiate themselves with the value add, yet keep the cost competitive. Way to do business!

John O.


One year later its still working as good as new! very happy with this product.


I got this to isolate my emergency brake disconnect battery from the main trailer battery. I would have preferred if the included wire crimps were the heat shrink type. Shipping took forever and was not trackable. Otherwise, this was a super easy product to install. Thank you etrailer for making it easy!


Great 'insurance' policy for any towed vehicle. It never fails... you get to your destination, you are tired, you jump in your towed vehicle and turn on the lights. Too late! The damage is done. If you haven't turned of the lights of your coach and your towed is hard wired to use it's own lighting as 'trailer' lighting, you NEED THIS DIODE. A breeze to install and a cheap failsafe .


No problems. Works as it should


Does what it's supposed to do. My warning lights do not come on anymore. That being said, it should be included or recommended for the Tekonsha brake controller system. I guess all vehicles don't have that problem, but why take the chance. I have a 2017 Toyota Highlander Hybrid.


I have a Class A Rv and it has a hydraulic pump on the brake lite switch. I was getting a back feed from the running light back to the pump. I installed this diode and it stopped the back feed. Works great and fast shipping from Etrailer. Thank you Ashley E. for all your help. I couldn't figure out what would solve this problem.


Fast free delivery, Installed very easily, works perfectly!
This product was installed to protect my roadmaster invisibrake system when using the Hopkins towed vehicle light kit on my 2015 Jeep Wrangler.


excellent i used this so i could run my 12 volt lights on enclosed trailer either of the 7 way or the on board battery in trailer


Installed the diode in-line coming off my brake wire to my tail lights to my third brake light on my 1941 hot rod. It keeps the turn signals, and running lights from ''feeding into '' my third brake light bar in my back window. Very easy to install.
I ordered two just because they are so handy to have around the shop.


Used in a trailer so the break away battery didn’t back feed the dump body battery or drain it. Both charged in series.


I had been looked for a towed vehicle lighting solution for a while and ran across this item on the etrailer web site. This is an easy to use product that is also economical. Installation was exactly as the package described - simple. Etrailer alsways has great prices and fast service. I've used them for all of my trailer parts needs for 5 years and will continue to be a customer.

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