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7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs

7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs

Item # C35FR
Our Price: $22.70
Trailer Wiring
Shipping Weight: 0.29 lbs
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Curt 7-way connector to 4-way or 5-way flat connector is designed for use on vehicles with Trailer Lamp-Out sensors when towing a trailer equipped with LED lights. Great Prices for the best trailer wiring from CURT. 7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs part number C35FR can be ordered online at or call 1-800-940-8924 for expert service.
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  • Reviews (57)
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  • Videos (2)
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CURT Trailer Wiring - C35FR

  • Wiring Adapters
  • Multi-Function Adapter
  • 5 Flat
  • 4 Flat
  • Plug Only
  • 7 Round - Blade
  • CURT

Curt 7-way connector to 4-way or 5-way flat connector is designed for use on vehicles with Trailer Lamp-Out sensors when towing a trailer equipped with LED lights.


  • 7-Way RV style adapter to 4-pole and 5-pole flat trailer connectors
  • Designed for use on vehicles with Trailer Lamp-Out sensors - such as Audi, Mercedes-Benz, Porshe, and Volkswagen vehicles with the factory tow package
  • Plugs into a 7-way connector on the vehicle and 4-way or 5-way flat connector on the trailer
  • 1-Year limited warranty

57004 Curt 7-Way to 4-Way and 5-Flat Trailer Adapter for VW, Audi, Porshe, and Mercedes-Benz Towing Trailers with LED Lights

Video of 7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs

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

Video Transcript for Curt 7-Way to 4-Way/5-Way Trailer Adapter Review

Hello neighbors. It's Brad here at etrailer. And today we're taking a look at the cut seven to four and five pole adapter. So as the name implies you are able to adapt a factory seven way to a four and five pole. And that's really nice because a lot of vehicles will have the factory seven way on there but maybe not the four pole. So if you look came to hook up to a trailer and realize that they have a four or five pole, you might be out of luck or have to run additional wire to permanently mount it.

Well, that's where this comes into play. So that's gonna allow you to be able to have your seven way, your four pole, as well as your five pole just with plugging into the factory seven lane. Now, sometimes your towing vehicle will not recognize the LED lamps on your trailer. And that's where this is great too as plugging that in is gonna allow this to send that signal to your vehicle making sure that your lights are actually working with your signals. So like our neighbor here they have a trailer with a four pole but they got a new vehicle that has a seven way.

So instead of having to run all new wiring for it you can simply plug this into the factory seven way. You can take your four pole and plug it in or if you have the same vehicle but you're towing a different trailer. This gives you that same ability. So having this is going to allow you to hook up electrically to those trailers. So now let's go ahead and test it.

So first I'm gonna start with my running lights. Next I'm gonna do my left turn signal, my right turn signal. And then finally my brakes. Now this neighbor also toes, a boat trailer. So having the five pole is gonna be really nice for the surge lockout as well as reverse light.

Now, for some of your foreign vehicles or high end vehicles that have LED taillights sometimes they don't have enough power to power the trailer lights. Well, this is gonna help with that. Allowing that to give it enough juice to be able to still retain your lights on the trailer. Something that's really nice about this is the size and that if you normally tow a seven pole you can simply swap this in whenever you're picking up a different trailer and need to hook up or really you can use this to hook up to any trailer. You have that ability and you can keep this in your glove compartment until you need it. And that was a look at the cur seven, two, four and five way adapter..

Customer Satisfaction Score:

Customer Reviews

7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs - C35FR

Average Customer Rating:  4.6 out of 5 stars   (57 Customer Reviews)

Curt 7-way connector to 4-way or 5-way flat connector is designed for use on vehicles with Trailer Lamp-Out sensors when towing a trailer equipped with LED lights.


Product as described and works as it should. I have this adapter on a 2008 Mercedes ML320 CDI and a 2008 Mercedes GL320 CDI. I have hooked both suvs into uhaul trailers with led lights and everything is working good.

Still Great after a year. I couldnt be happier! Great for cars with no led lights to hook up trailers with LED lights
Dini - 07/03/2023


Was having a dilemma about how to address the hyperblinking and other issues with my trailer LED lights. This worked perfectly, and was quick and easy. Seems to be a well constructed product as well. 2021 Sprinter


I ordered a series of parts to use a hitch extender for my truck camper. The process was easy, the online specs and details ensured I ordered the correct parts. Everything works as advertised a year later. I’m pulling a 16’ enclosed Sure-Trac trailer for my UTV and it lights up the night. Thanks etrailer for an easy process.


Doesn't work with my 2021 GMC 3500 HD Sierra. The 7 way works with trailers but I can't get the adapter 4 way to work with LED lights. The truck sees that there is a "trailer" attached but the LED's don't work. If I put the LEDs on a 12V battery they all work brilliantly.

Called CURT. They didn't know what would allow LEDs to work with my truck.

Looking for a solution.

A simple and perhaps silly thing to do would be to make sure that everything is properly seated on both the trailer side and vehicle side. Additionally, this part does have a one year limited warranty you may want to look into if making sure things are plugged in all the way doesnt help.
-- Etrailer Expert Brooke M - 08/03/2022


Worked perfectly


Perfect match. Great quality.


Fixed the issue I had with my Mercedes GL550 not switching to towing mode and enabling all the LED trailer lights!


Did not work as advertised, Requested r efund.

I wanted to reach out and see what was not working with the adapter? I would like to see if I can help.
-- Etrailer Expert Jenny N - 05/02/2023
The adapter is supposed to work for cars that pull a trailer with LED lights, I plugged it in, and nothing. I plug in non LED lights and it works. How do I go about sending it back for my refund? I put in a request and haven’t seen a email regarding it.
-- comment by: Greg - 05/03/2023
I will have our Customer Service team contact you about returning the adapter.
-- Etrailer Expert Jenny N - 05/03/2023


Questions quickly answered on line and fast shipping


quick service and delivery, good consultation and the product worked perfectly!


This solved my tow light issues when connecting a LED light to a Volvo XC60.


2012 Mercedes. Works as it should with lcd lights


Plugged in. Works. Nice!

Works great. No issues.
Bob F - 11/29/2022


Product ended up not working very well - the funky. chinese wiring was not a straight forward hook up and i got the lights to eventuLly work, but even with an adapter it sets off the lights out computer in my car and i get no brake lights .


Works great on my 2008 ML320 oem traile r.


Problem solved! I had ordered a set of the Blazer wireless LED trailer lights for the towed vehicle behind my motorhome. They didn't work. After trying another set that didn't work then calling the manufacturer I was about to give up. However, thanks to Tommie C at etrailer, he recommended this adapter and it resolved the issue. etrailer is the BEST! Great products, great customer service, great technical support.


I recently purchased this product and it solved the light monitoring system errors that I was having with my 2012 BMW X5. My trailer was equipped with LED lights and the adapter was the perfect solution.


Solved the issue of German auto with LED taillights on a trailer.


Great service and prompt delivery!
7 pin trailer light connector works great and allows me to connect easily to my older wire harness.


The customer service was excellent! I had a question about a lighting system for my tow vehicle and RV. I was directed to a match and they were correct. Not only does it work, they didn’t recommend the highest priced item hence saving me money.


Great service


High quality; fits well


Works great. Solves the problem of LED lights triggering faults on our BMW X5. The lights work and the car electronics don't signal any faults and switch the rear parking sensors off as designed.


Roger in Customer Service was simply excellent. Been trying to get a special adapter for my trailer for months (floating on some ship in the Pacific!). He persisted with two suppliers and one showed up today!! He even asked if I wanted to cancel the other order. Really on top of things and found this to be true with this company.


This item arrived quickly and on time. Product as described and fixed my issue with my 2020 truck not picking up LED light on my trailor. I spent 60000 on a new truck and have to buy this to get my trailor to work properly. Chevy should be ashamed of themselves! Glad they have products like this.

Show More Reviews

See what our Experts say about this CURT Trailer Wiring

  • 7-Way to 4-Way Adapter that Can Fit 2021 Volvo V60
    Yes the 7-Way to 4-Way adapter # C35FR would fit the 7-way of your 2021 Volvo V60 and would be a great and easy way to convert to a 4-way like you are wanting.
    view full answer...
  • Is Curt 7-Way to 4-Way/5-Way Trailer Adapter Also Compatible With Incandescent Lights
    Yes, the 7-Way to 4-Way/5-Way Trailer Adapter # C35FR can be used with trailers that have LED and incandescent lights. There will be no need for an additional adapter for your 2014 Porsche Cayenne.
    view full answer...
  • Can Curt 7-Way to 4/5-Way be Used with Just 4-Way
    Yes, if you used the Curt 7-Way to 4/5-Way part # C35FR with a 4-way it will work just fine. The 5th pin of the adapter would basically just not get used which has no impact on the other 4.
    view full answer...
  • Troubleshooting LED Lighting on Trailer Not Working Behind a 2006 Land Rover LR3
    Unfortunately, it sounds like there may be an issue with either the wiring or the control module on your 2006 Land Rover LR3. As you have tried the 7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs # C35FR as well as adding resistors with both failures to operate the lights. It only stands to reason the vehicle has something going on with it that it is not recognizing you have a trailer connected.
    view full answer...
  • Will The Curt Adapter C35FR Work On A 2024 Audi Q8
    Yes, the Curt adapter # C35FR is exactly what you will need to use on your 2024 Audi Q8. Certain vehicles, Audi included, use lighting that works at low/varying voltage, and have lamp out sensors that may go off. This adapter will allow your trailer lights and vehicle lights to work normally when towing.
    view full answer...
  • Recommended Trailer Adapter For Vehicles With Lamp Out Sensors For 2008 Infiniti FX35
    It sounds like you are looking for a trailer adapter for a vehicle with lamp out sensors for your 2008 Infiniti FX35. If that is the case I recommend the 7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors # C35FR if your trailer has a 4-way or 5-way connector, or the Trailer Connector Adapter w/ Lamp-Out Sensor Bypass # 20142 if your trailer has a 7-way connector. These sensors are commonly needed on German vehicles with lamp out sensors, or newer domestic vehicles...
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  • Adapter Needed To Tow A Trailer With LED Tail Lights With a 2011 Mercedes-Benz ML550
    To make the LED trailer tail lights work with the factory trailer wiring on your 2011 Mercedes ML550 you will need a Trailer Connector Adapter w/ Lamp-Out Sensor Bypass # 20142. This will plug into your 7-way on your ML550 and allow the trailer to plug into it. The adapter tricks the computer in your Mercedes to believe that the trailer does have normal incandescent bulbs so that you do not get the bulb out error on your dash. If you are hauling a smaller trailer the 7-Way to 4-Way/5-Way...
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  • Trailer Lights Won't Work on 2011 Mercedes-Benz GL on Trailer With 4-Way
    I'm not sure why U-haul would say it's fine when it clearly isn't, but the problem with the Mercedes is that there isn't enough power draw, so you'd need to use a lamp-out adapter: - 7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors # C35FR This will allow the trailer's brake and turn signals to recognize the signals coming from your Mercedes. If you were already using one of these adapters (I wasn't sure if you were talking about one of those or a 4-way to 7-way...
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  • Troubleshooting 2014 Volkswagen Touareg Not Recognizing Trailer With LED Lights
    Based on what you are describing yes, the 7-Way to 5-Way/4-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs # TR20141. The Curt # C35FR will also work. The problem is likely that the LED signals from your trailer are not being read by your vehicle's computer. Adapters like this one use built-in resistors to solve that problem. If you need a 7-way the Curt 7-Way Trailer Adapter for Towing Trailers with LED Lights # C57003 is also available.
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  • How to Draw Enough Power When Using LED Lights on a 2023 Ford Transit
    It is not uncommon for LED lights to not draw enough power for the 4-way or 7-way to work properly. If the # H01540 lights are not working when plugged into your 2023 Ford Transit, that is likely the cause. If you have a 7-way, you could use the 7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs # C35FR to correct this issue. If you only have a 4-way, you would want to add the Load Resistor Kit # DI34ZR to each of the light wires on the light...
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  • Pulling a Trailer With LED Lights and the Vehicle is Reading Lamps Out
    Though we do recommend having a resistor on each LED light, we do have other options as well. Since you mentioned having a 7 Way connector, you could use a lamp out sensor adapter like the # 20142 if the trailer is wired with a 7 Way plug or a # C35FR if you have a 4 Flat or 5 Flat plug on the trailer. These have all the needed pieces to trick the vehicle's computers into working with LED lights on the trailer. That being said, you could spice resistors into each of the wires attached...
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  • Options to Replace Atwood 82543 Hydraulic Brake Actuator
    The Demco Hydraulic Brake Actuator part # DM72VR is for drum brakes which is what you need to replace an Atwood 82543. The other options you're inquiring about are for disc brakes which won't work. In short, there are tons of different versions of the Demco Hydraulic Brake Actuator each with different features such as drum/disc brake compatibility, weight capacity, ball size, lockout type etc. The correct one for the Atwood 82543 is listed above. In order to reverse without the brakes...
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Info for this part was:

Employee Lindsey S
Edited by:
Lindsey S
Employee Jeff D
Installed by:
Jeff D
Employee Bradley B
Installed by:
Bradley B
Employee Jameson C
Expert Research:
Jameson C
Employee Jacob T
Video Edited:
Jacob T
Employee Dustin K
Video by:
Dustin K
Employee Wilson B
Updated by:
Wilson B
Employee Noah M
Updated by:
Noah M
Employee Kristina F
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