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Roadmaster Single Park Light Diode
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Roadmaster Single Park Light Diode

Part Number: RM-690
141 Reviews | 171 Questions
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2003 jeep wrangler accessories and parts roadmaster flat tow wiring harness 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







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Video of Roadmaster Single Park Light Diode
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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:

Ratings & Reviews

4.7

141 reviews
5 Stars
(116)
4 Stars
(19)
3 Stars
(1)
2 Stars
(2)
1 Star
(3)
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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.
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Jacob profile picture

Jacob

6/7/2025

The diode has been installed on my truck for a year now. Still working great. Still very happy with it.

Kate F. profile picture
Etrailer Expert

Kate F.

6/9/2025

@Jacob Glad we had the right part to get your brake controller working as it should Jacob. Good choice with the Roadamaster diode, they are definitely built to last. What kind of trailer are you pulling with the Chevy? Fun trailer, work trailer, or maybe a little of both.....
by:
Works great to isolate my 12 volt charger wire from my truck to my camper. Installed it on the camper side. My truck was sensing low battery from the trailer and disconnected the trailer brakes. The solar on the camper will do the same if it is trying to charge more than the alternator on the truck. Newer trucks are computers on wheels. They do not like other electric components that they are not made with. This part did the trick no problems after 1500 mile trip with the camper.
by:
Worked great! Used it with a 15amp slow breaker on my charge line for flat towing my wt Maverick.
by:
I have only received the diode and installed it, I have not pulled the trailer yet. Connection was quick and easy with suppled connectors.
by:
Product arrived as promised - will install soon, thank you for the fast shipping.
by:
Worked perfectly to add the Right and Left front parking lights to lighting when car is being towed. I ended using the dual input version and will keep these for future use.
by:
Works as needed
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.
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by:
Worked well to not drain my truck battery down
by:
Very nice product. Completely sealed aluminum housing is high quality. It was just what I needed to prevent back feed on the battery charge wire between my towed jeep and motorhome.
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.
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Greg S.

10/9/2018

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

by:
Work great, perfect thank you.
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:
Product is working great
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:
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:
Just what I needed. Thanks for the speedy delivery.
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:
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:
Great part, makes everything work as it should.
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:
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Ronald

2/6/2022

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

by:
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 .
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See what our Experts say about this Roadmaster Accessories and Parts

Do you have a question about this Accessories and Part?
  • 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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  • 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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  • 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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  • Specifications for Roadmaster Diodes # RM-690 and # RM-790 for Use on a Semi-Trailer
    I do have some technical information for you about the Roadmaster Diodes # RM-690 and # RM-790, but I do not have any prints available. Both part numbers are 1/2" tall, 1-9/16" wide, and are 1-5/16" long. They can withstand up to 85 of continuous amps, plus they have been tested to work when they are frozen and tested in an oven up to 180 C without failing. My contact at Roadmaster said that these can definitely take a beating and will work great for your application.
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  • 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 Prevent Electric Over Hydraulic Actuator From Drawing Power from Trailer Battery
    Hey Steve, to avoid having the trailer battery power the actuator of the Hydrastar kit part # HYD44VR you would want to install a diode that only allows the current to go to the battery and not from the battery back to the actuator. For that you'd want the part # RM-690.
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  • Will Integrated Brake Controller of 2025 Chevy Silverado 3500 Detect Electric Over Hydraulic Actuatr
    Hey Ken, it should detect the brake style and work automatically. But if your trailer has a solar setup let me know and there may be some extra steps.
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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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    Image 1 for
  • How To Prevent Backfeed On Tail Light Wiring When Using Hopkins 7 Way Round Pin To 7 Way Flat Pin
    Hey Ron, what made you decide to install that converter? The reason I ask is that a converter like the Hopkins 48845 is normally only needed when the tow vehicle has separate brake and turn signal wires, and the trailer uses combined brake/turn circuits. The converter takes those separate brake and turn signals and combines them so the trailer lights work correctly. In this case, both the 7-way round pin and 7-way flat blade connectors should already be using combined stop/turn circuits...
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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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  • Troubleshooting Parking Tail Lights Staying On In 2025 Grand Cherokee After Flat Tow System Install
    Hi Mark; the # RM-690 diode can be used to prevent backfeeding on the affected circuit. It only allows power to flow in one direction, so if the issue was caused by voltage backfeed into the Jeep’s taillight circuit the diode will correct it. The auto-reset breaker/fuse is only there to protect the wiring from an overload condition, it does not prevent backfeeding. Since the problem started after driving in rain, and you're already replacing the 6-way connector, there is a good chance...
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  • 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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  • 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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  • Looking for Single Diode for Freightliner Chassis Motorhome
    Hey Ken, we have exactly what you are looking for with the Roadmaster single diode part # RM-690. This has a single in and out and will prevent backfeeding like you need.
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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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  • 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 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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  • How to Prevent Backfeeding On Charge Line Kit
    Hey Greg! None of the kits specifically come with a diode to stop backfeeding. All you need to do is get a charge line kit like # RM-156-25 and then add in a simple diode # RM-690 on that circuit to prevent this issue. What are you setting up to flat tow?
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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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  • How To Install A Single Feed Diode To Prevent Backfeeding
    Hi Robert, Diodes like the Roadmaster Single Park Light Diode # RM-690 you were looking at simply get spliced inline with whichever light function you're wanting to prevent feedback on using the included spade terminal connectors. You'll want to place the diodes close to the light to limit the amount of room for feedback.
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  • What Gauge Wire To Use For Power Wire On 7-Way?
    Hello Vincent, thanks for reaching out. Some 14 gauge wire would be acceptable for the 12v power wire. Generally, we would use a 30 amp circuit breaker for this. To prevent any backfeed you can install a diode like part # RM-690. I hope this helps. Leave a reply with any other questions or comments and I will get back to you.
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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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  • Difference Between Roadmaster and Curt Tow Bar Wiring for 2019 Jeep Wrangler
    Hey Dianne! I'm glad you came back and clarified because I just read your first submission and I really wasn't sure what the question was. The 2019 is in fact the JL, which started production in 2017. I'm assuming you were looking at the Roadmaster # RM-154 and the Curt # C96JR. The Roadmaster looks different and has the separate diodes because it is a universal kit. The Curt is custom for your vehicle so it will be the easiest installation, completely plug and play, with no additional...
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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.
    view full answer...


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Info for this part was:

Employee Mike L
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Employee Jameson C
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Employee Jeffrey L
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