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Roadmaster Single Park Light Diode
Roadmaster

Roadmaster Single Park Light Diode

Part Number: RM-690
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$19.91
Retail:$28.94
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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 The Low-Down on the Roadmaster Single Park Light Diode

Hello everybody, this is Jeff at etrailer.com. 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   (108 Customer Reviews)


by:

Just what we needed at a great price. Very fast shipping.
Thanks.



by:

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 .



by:

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.



by:

Used for isolating the car battery from the trailer battery.



by:

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.



by:

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. profile picture

Greg S.

10/9/2018

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



by:

It did exactly what I needed it to



by:

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 .

Craigc profile picture

Craigc

11/14/2016

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



by:

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.

Cbtraveler profile picture

Cbtraveler

12/19/2017

Product is still working fine without any problems



by:

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. profile picture

John F.

9/9/2020

It still works as intended with no problems.



by:

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.



by:

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!



by:

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.



by:

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.



by:

Ronald profile picture

Ronald

2/6/2022

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



by:

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. profile picture

John O.

4/25/2018

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



by:

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!



by:

Worked perfectly, just needed to buy 4 more!



by:

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.



by:

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.



by:

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.



by:

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.



by:

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.



by:

Diode itself seems fine. But the connectors were loose fitting and the sleeve that fits over the wire was either too thin or too soft. As a result, when crimped onto the wire, the wire was still loose and came out with a light tug. Replaced the connectors with better ones. Is now working fine.



by:

This diode done extremely well for my application. Used it on my box trailer. Made it where when I go to back up the strobe lights com on with the back up lights and horn and the horn or the back up lights will come on when I use the switch for the strobes


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See what our Experts say about this Roadmaster Accessories and Parts

  • Troubleshooting Trailer Battery Backfeed on 7-Way Auxiliary Circuit
    Hi Ron; since the light remains on when you're not hooked up to the 7-way on your vehicle it indicates that a power backfeed from your house batteries like you said. This happens sometimes depending on how things are wired. The easiest solution is to add in a diode # RM-690 which will keep the power from running to the connector and powering the LED.
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  • How to Wire the GloLight LED Trailer Tail Light Part # STL178RB to a Trailer Connector
    The white wire on the back of the GloLight LED Trailer Tail Light part # STL178RB is for the ground. If you were wiring it to a trailer connector like part # HMC20031 then you would just need to make sure that it is attached to the ground terminal and no additional grounds would be needed. The outer ring of the light that you are referring to is made of plastic just like the body of the light is. The wire leads are around 6" long. I have attached a review video for you.
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  • Does Roadmaster Diode RM690 Prevent Overcharging
    Hey Walt, know the Roadmaster diode part # RM-690 does not have any over charge safety features. With that said most of the time the charge coming through this diode isn't going to be strong enough to really significantly over charge anything.
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  • Yellow Charge Light On Hopkins Engager Stays On with Trailer Disconnected
    In regards to the Hopkins Engager Push-To-Test Trailer Breakaway Kit part # 20099, the first issue that you described of the yellow charge light being on even while disconnected from the tow vehicle could either be a short in the circuit board or if the trailer has an auxiliary battery this is then feeding the breakaway battery and in which case you would need to install a diode part # RM-690 to prevent this. The issue with the yellow charge light illuminating when the battery test button...
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  • Which Way Should Diode Point on Highlander for Install of Brake Controller
    Yes you need the diode arrow to point towards the brake controller. That will allow the voltage to travel into the controller but not backfeed back on to the Highlander in any way. If you need a diode we have the part # RM-690.
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  • Troubleshooting Lack Of Brake Controller Output With A 2025 Chevy Silverado 3500
    Have you tested the brake controller output on the 2025 Silverado's 7-way and confirmed that it's sending power back to the trailer when the manual override is being activated? When you say the brakes aren't activating as they should do you mean they some times activate or are weak or that they're just not activating at all? Does your Silverado have trailer detection and if so is it detecting that the trailer is attached? I would start by testing your 7-way with a multimeter # PT89ZR...
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  • How to Prevent Battery Backfeeding and Breakaway Battery Charging Off Trailer Battery
    Hi David; this is pretty common and all you really need is to throw in some simple diodes # RM-690. These will only allow power to flow in one direction so it will stop any backfeeding and power drain. It sounds like everything is in-line so you can put one between the breakaway battery and your trailer battery and then one between the batteries and the tow vehicle.
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  • Diode for Pre-Collision Malfunction When Installing Brake Controller in 2018 Toyota Highlander
    Yes, you can use the Roadmaster Single Park Light Diode # RM-690 with a Hopkins Reliance brake controller on your 2018 Toyota Highlander. The issue is the backfeeding with the Pre-Collision System (PCS) so you want to install this diode to the wire that connects to the cold side of the stop light switch (which is generally the red wire).
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  • How to Wire the Roadmaster Single Park Light Diode # RM-690
    Wiring in the parking light diode # RM-690 is easy. All you have to do is locate the wire leading to the parking light bulb. Cut the wire and insert the diode in-line with the wiring. The IN side will be the part of the wire that leads to the front of the vehicle. The OUT side goes to the bulb. Using these diodes prevents back feeding problems when using a supplemental braking system. I included a picture showing how you would wire the diode.
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    Image 1 for
  • How to Install Roadmaster 690 Diode to Fix 12V Power Issue on 2024 GMC Sierra Denali
    Thanks for reaching out, Jim! The Roadmaster Single Park Light Diode # RM-690 will work great for this application, and I'm glad to hear others have been successful using it! You'll want to install the diode on the wire connected to the 1 o'clock position on your 2024 GMC Sierra 3500 7-Way socket (see attached photo). I'm unsure of what the wire color will be, but you can either disassemble the 7-Way to get at that wire, or you can use a Circuit Tester # PTW2993 to probe for the wire...
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  • Battery Connection for 6V Vehicle and 12V Accessories
    If I am understanding correctly you want to run two 6 volt batteries in series to get your 12V output. This will work well and allow you to also run a 12V battery with those two 6V batteries, when you then connect the output power 12V of the two 6V batteries in parallel with your 12V battery. The issue you will have is separating the 6V you need for your kit car. A 12V battery can start a 6V starter with precautions, but the issue would be the constant 12V power going to your light...
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    Image 1 for
  • Converter Wiring Harness Needed For A Third Brake On A 1990 Ford Bronco II
    Hey Keith, You could use the Vehicle to Vehicle Tail Light Converter # 118158 you were looking at and connect the stop function to the third brake light and just cap off the the left and right turn signal wires on the output side since you won't be using them. You can install a diode # RM-690 between the light and converter to prevent any electrical feedback from the light.
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  • Why Would Brake Controller Cause Vehicle Brake Lights to Periodically Come On
    That has to be a brake controller issue. Sounds like the controller is backfeeding the stoplight circuit it taps into as a signal wire with voltage which is then activating your brake lights. When this happens the brake controller is in need of being replaced. For a brake controller replacement I would recommend the Prodigy P3 Brake Controller part # 90195. This is our best selling brake controller because of how well it works and how easy it is to setup. This is a proportional brake controller...
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  • Are Extra Diodes Needed to Use InvisiBrake with Hopkins Harness on 2015 Jeep Wrangler Unlimited
    The Hopkins wiring harness # HM56200 has diodes that protect the car but will not prevent back feeding to the InvisBrake, # RM-8700. To use the Hopkins harness and InvisiBrake together you would have to install 3 additional diodes, # RM-690, on the Hopkins harness between its diodes and where the InvisiBrake ties into the harness. You will need one diode each on the green, yellow, and brown wires. But if you are going through all of that you might as well install diode kit # RM-154.
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  • How To Install A Roadmaster Hy-Powered Diode On Trailer 7-way
    Hi Randy, Are you just trying to charge the trailer batteries from the tow vehicle's 7-way? If so you're using the 12v aux pin on the 7-way and could place the diode on the trailer side just before the junction box to prevent any current from backfeeding to the tow vehicle. The face of the diode has an "in" and "out" labeled on it. The "in" will be power coming in from the tow vehicle. The "out" would be the power going to the batteries. With these diodes current can only flow from in...
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  • Troubleshooting Brake Controller Install that Causes Error Code When Override Lever is Applied
    We have the # ETBC7 which would be the kit you'd need to make the conversion to a 7-way from a 4-way, but we do not have a different kit wth a brass socket or anything really similar. The 7-ways do last surprisingly long. The double edged sword to using one that has a gasket to seal the lid is that if moisture does get in it's trapped and wouldn't easily evaporate.
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  • How to Prevent Trailer Breakaway System Battery from Overcharging and Back Feeding Into Tow Vehicle
    The correct way to fix this would be to install a battery charger like # 20011 on each of your break-away systems. This is a reasonably priced option that will prevent the overcharging of your breakaway battery and will also prevent the back feeding your describe. The installation is simple, as you can see in the linked video.
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  • Where Would Diode Need to Install on Brake Controller If it Was Needed
    If you had a vehicle that needed a diode installed when installing a brake controller you'd need to install the diode like part # RM-690 on the red wire of the brake controller. This prevents the brake controller from back feeding onto the vehicle wiring when the manual override lever is slid.
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  • Tail Light Converter Between Class C With Combined Lights And A 2006 Mazda MX5 With Separate Lights
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  • How To Charge Vehicle Battery Using Trailer Battery While Hooked Up To Shore Power
    The purpose of a diode is to stop the back flow of electricity. I can honestly say I have never heard of someone wanting to run a charge line from the trailer battery to the vehicle battery but I'm sure it would be possible. That said, when you attach two batteries to one another via a charge line they will try to balance each other. Therefore, if the start battery has more juice than the trailer battery the trailer battery will pull from the start battery and vice versa. The diode however...
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  • Recommendation for Wiring Breakaway and Marine Battery on Enclosed Trailer
    For your enclosed box trailer, it is best to let the breakaway battery run the breakaway system and use the accessory battery to power your trailer's interior lights (or other parts). This is the best option because your breakaway battery needs to be completely charged at all times and it's possible that the interior lights can drain the battery of the trailer. As you mentioned in your question, when charging two batteries on the same circuit, there is the potential for draining both....
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  • Can Roadmaster Diode Be Installed to Prevent Curt Breakaway Battery From Draining Onboard Battery
    Thanks for all of the information about what you're experiencing with the Curt Push-To-Test Trailer Breakaway Kit # C52042. I'll address your questions in the order you asked them: 1 - The built-in battery charger that comes with the breakaway kit will prevent it from overcharging. 2 - Using the Roadmaster Single Park Light Diode # RM-690 is an excellent way to prevent back feeding like that you mentioned. 3 - The application is pretty simple and effective so there isn't anything else...
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  • Diode for Installation of Brake Controller on 2018 Toyota Highlander
    Yes, you will likely see the issue of the malfunctioning Pre-Collision System (PCS) on your 2018 Toyota Highlander with the Tekonsha Primus IQ Trailer Brake Controller # TK90160. So you can do is the Roadmaster Single Park Light Diode # RM-690.
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  • Isolating Auxiliary Battery From Draining Break Away Battery
    You can isolate the break away battery from the auxiliary battery using the Battery Isolation Solenoid # PK5231201. The auxiliary power supply that is needed on this solenoid can be the running lights of your trailer. That way, when your trailer is connected, you can charge the break away and the auxiliary trailer battery, but when not connected the break away battery will not be drained by the auxiliary trailer battery. So the 12V comes into the trailer and runs to the aux trailer battery...
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Info for this part was:

Employee Mike L
Expert Research:
Mike L
Employee Michael H
Expert Research:
Michael H
Employee Jameson C
Expert Research:
Jameson C
Employee Jeffrey L
Expert Research:
Jeffrey L
Employee Andrew K
Video by:
Andrew K
Employee Jeff D
Installed by:
Jeff D
Employee Jacob T
Video Edited:
Jacob T
Employee Randy B
Test Fit:
Randy B
Employee Wilson B
Updated by:
Wilson B
Employee Hannah L
Updated by:
Hannah L

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