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Curt Trailer Connector Adapter - 4-Way to 7-Way RV and 4-Way Flat

Curt Trailer Connector Adapter - 4-Way to 7-Way RV and 4-Way Flat

Item # C57672
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This multi-function, vehicle-end connector converts any 4-way flat, vehicle-end plug to a combination 7-way outlet and 4-pole flat outlet. Lowest Prices for the best trailer wiring from CURT. Curt Trailer Connector Adapter - 4-Way to 7-Way RV and 4-Way Flat part number C57672 can be ordered online at or call 1-636-306-4830 for expert service.
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CURT Trailer Wiring - C57672

  • Wiring Adapters
  • Multi-Function Adapter
  • 4 Flat
  • 7 Round - Blade
  • Plug and Lead
  • 4 Flat
  • CURT

This multi-function, vehicle-end connector converts any 4-way flat, vehicle-end plug to a combination 7-way outlet and 4-pole flat outlet.


  • Adapts 4-way flat to both 7-way RV and 4-way flat
    • 4-Way flat output connects tail lights, brake lights, and turn signals
    • 7-Way connects tail, brake, reverse, turn signals, and auxiliary power
  • Dust covers keep connectors clean when not in use
  • Split loom keeps wires contained and well protected
  • Simple installation
    • Wiring harness plugs into existing 4-way flat connector and hardwires to existing wiring to get additional functions needed for 7-way
  • Included hardware and metal mounting bracket secures wiring to the vehicle or trailer hitch
  • 1-Year limited warranty


  • Distance between bracket mounting holes center to center: 2-1/4"
  • Harness length: 17"
  • Yellow wire is for reverse lights
  • Blue wire is for brakes
  • Black wire is for 12 volt power
  • White wire is ground

57672 Connector Diagram

57672 Curt Multi-Function Socket - 7-Way RV Blade and 4-Way Flat - Universal Fit

Installation Details C57672 Installation instructions

California residents: click here

Customer Reviews

Curt Trailer Connector Adapter - 4-Way to 7-Way RV and 4-Way Flat - C57672

Average Customer Rating:  4.7 out of 5 stars   (307 Customer Reviews)

This multi-function, vehicle-end connector converts any 4-way flat, vehicle-end plug to a combination 7-way outlet and 4-pole flat outlet.


Overall, satisfied. The installation videos were helpful, and the product seems quality. I only have one complaint, which is what kept this from being a 5 star review. This may be obvious to most people, but it wasn't to me. This WILL get you to a 7 pin connector, but there is a good bit more work to do to get all the functions of a 7 pin connector to work. Meaning, to get power to my 7 pin connector and trailer, I had to run a wire to the battery, and place a circuit breaker inline with that wire. Again, this may seem obvious to some, but it took some figuring out for me, and any time I asked this question to etrailer, they could never seem to give a straightforward answer. But for my Mazda CX-5, about 15 feet of 12 gauge wiring and a small fuse kit did the trick. Lots of splicing of course.


I took my car over to the dealership and they sent it out to another shop. When he brought my car back, the electrical wires were installed upside down. It took the installer over 6 hours to install my receiver hitch.
It looks great now that I’ve turned the wiring the correct way to install your electrical wiring.


Put this on after #c56027 to change to 7-way rv plug as all my trailers have been switched to 7-way. 7-way is much easier to plug and unplug than 4-way. Easy to install. I have been using it once a week and it is working very well.


This sure made changing from the factory 4-way connector to a 7-way/4-way connector quick and easy. All I had to do after installation was to add wiring for the electric brakes and trailer battery charging.


Not even 2 years after install all rusty. Electric brake pin broke due to rust.
Impossible To remove 4 bolt holding connector due To rust. I do not recommend

Its unfortunate that your pins and bolts are unusable due to rust. I see that you are located in Canada, we recommend making sure that you are using dielectric grease often to prevent and keep the rust from spreading along the harness. Unfortunately, rust is not covered under warranty, and even if it was, this is well passed the one-year warranty for this item. I would recommend contacting our customer service department for them to assist you in ordering a new harness, such as part # 118467
T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
-- Etrailer Expert Katrina B - 07/19/2022


I used this on my 2017 RAV4. This harness provides me the flexibility of using flat-4 or a 7 way connector for towing flexibility. The RAV4 is a small tow vehicle and I like the added security of electric brakes even on lighter single axle trailers which the 7 way allows. I plugged this adapter into the flat-4 connector provided by the "T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector Item # 118578" and used heat shrink tubing around the crimp connectors for the brake controller wires to keep moisture out.


I took it with 2 bikes loaded on a maiden voyage. We traveled on a highway with a lot of bumps because of repair work in progress. It preformed great! Minimal movement of the bikes and the carrier. The whole carrier is very solid. It’s simple to load and unload. I’m very happy with this carrier.


Your site us very helpfull for information and support and i reallt apreciate etrailer for all tge purpose.good product ,help support,and fait delivery even heure in Canada.
Tgank to all of your team.i am presently installons the controller on my car after the installation i Will feed about how it work.
Have a nice day


This kit had everything I needed to wire my van to tow with a brakes. It's pretty straight forward and easy to install


Installation was easy and intuitive. This fit my 2008 Subaru Outback wagon with zero problems. The hardest thing was removing the muffler hangers, but a little penetrating oil and channel locks made that much easier.


Perfect fit and easy to install. The only thing I would change is the 4 way flat connector tends to fall out of its holder. Not a big problem. It just need a little help to keep it in place.


This would be a 5 star rating if all my trailer plugs fit equally well. The preformed trailer wiring plugs are a perfect fit, (4 out of my 6 trailers have them), but two aftermarket plugs are a struggle to get the retention notch to fit inside cover hook that keeps the plug in place. ((Otherwise the plug pops out)).
Bottom line is I would buy this connector again because of the price point and ease of installation. From now on I will be buying the preformed trailer wiring harness for the perfect fit.


I was fortunate to be one of the ones to order and eventually receive a 2021 Ford Bronco First Edition. Strangely enough, that meant that I was not able to order certain accessories with it one being the Tow Package. I contacted etrailer and explained what I was trying to do (hitch and 7Pin and they sent me a list of everything I needed to make it work


Worked out good, but pigtail could be slightly longer


The reason why I bought this is because I have reverse lights on my trailer should work good haven’t tried it yet


I would really like to give 5 stars, but can't. They have great videos on Installation, but none on New Jeep Wranglers. Can't figure out the Wire for Brake switch , so I'm Stumped unless I want to pay Dealer a crazy amount Green.


the 7 to 4 adapter it’s not specific for this car and hitch. the tongue to open the lid stick out to far not allowing the removable car bumper cover to fit.I had to cut the tongue of the lid in order to fit the cover

Thank you for your feedback. You can use a mounting bracket like part # C57202
Curt No-Drill Bracket for 6-Way or 7-Way Round Trailer Connector Mounting Bracket - Long
to attach the harness to the hitch versus using the bumper.
-- Etrailer Expert Jenny N - 11/09/2021


It works as advertised. There is no hole for the mount bracket, so you have to drill your own.


Fits and functions as designed.


Bought the connector to replace an identical one damaged last winter. Same great quality and installation was a breeze.


Needed to slightly modify the bracket clearance holes to have the plastic holes line up properly and fit cleanly. Not a big deal but someone else may have struggled with that if they expected a simple install.


Wasn't sure what I needed or where to find an installer. My customer service agent/agents where exceptional. They all took time to provide information I needed to make the correct choices.


Got the order quick I will be installing it in the next day or two but it seems very well made and a simple DIY install.


It delivers the advertised functionality and was easy to install.


Super easy install. Their installation video covers everything.piece of cake.
2016 Outback. Great first step in adding a 7way plug and brake controller.

Show More Reviews

See what our Experts say about this CURT Trailer Wiring

  • How to Use a 4-Pin to 7-way Trailer Connector Such as C57672
    The # C57672 will allow you to convert an existing 4 pin connector on a vehicle and allow it tow a trailer that has a 7-way. By attaching the mounting bracket to the underside of the bumper or chassis of the tow vehicle, plugging the 4 pin on the adapter into the existing 4 pin connector on the vehicle and attaching the white ground wire to the tow vehicle's frame or chassis, you'll be able to activate the lighting functions on your trailer. There will be three remaining wires on the adapter...
    view full answer...
  • Can 4 Way and 7 Way of Curt Trailer Connector Adapter # C57672 be Used at Same Time
    Yes, the 4-way and the 7-way of the Curt Trailer Connector Adapter # C57672 that you referenced can be used at the same time as they are both active at all times.
    view full answer...
  • How Does 7-Way Trailer Adapter with 4-Way Connector Install
    What you have pictured is a 4-way to 7-way adapter similar to part # C57672. The male side 4-way connector plugs into a vehicle side (female) 4-way to convert the vehicle's connector to a 7-way. The existing 4-way on the vehicle only has the lighting functions so the rest of the wires need to be hardwired to make the 7-way completely functional. The additional wires are to power reverse lights (yellow), the 12 volt auxiliary pin (black), and electric brakes (blue). The white wire is...
    view full answer...
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  • Do the Blue, Yellow, and Black Wires Need To Be Run On the Curt Trailer Connector Adapter C57672
    For starters, we do not offer products through Amazon as they are a competitor of ours. However, I can offer you the Curt Trailer Connector Adapter part # C57672 which will work on your 1968 Ford F-150 if you have an existing 4-way trailer connector. The additional black, yellow, and blue wires do not need to be attached in order for the trailer light to work but you will need to ground the white wire to your frame. The black wire is to charge a battery on the trailer and you will need...
    view full answer...
  • Does Ground of 4-Way to 7-Way # C57672 Have to Be Ran for Just Taillight Functions
    If you were only planning on using the standard trailer taillight circuits with the # C57672 you would not need to run the extra ground wire although it wouldn't be a bad idea as it would add additional grounding to your trailer wiring. If you wanted to connect it you'd want to run it to the vehicle frame.
    view full answer...
  • Does 7-Way Adapter C57672 Have 4-Way Functions on 7-Way
    Yes, the 7-way adapter part # C57672 does give you the exact same features as the 4-way on the 7-way as well as this has a second 4-way on the side of it as well.
    view full answer...
  • Which Battery Terminal Do I install Black Wire Of Curt Trailer Adapter On My 1991 Ford
    Per instructions when installing The Curt Trailer Connector Adapter # C57672 on your 1991 Ford the black power cable will need to be attached to the red positive terminal on your battery per the instructions. This multi-function, vehicle-end connector converts any 4-way flat, vehicle-end plug to a combination 7-way outlet and 4-pole flat outlet. I attached a review video link below.
    view full answer...
  • How to Install 7-Way Connector on 2019 Subaru Outback Wagon
    We have exactly what you need to install a 7-Way connector on your new 2019 Subaru Outback Wagon so you can connect with the 7-Way on your trailer. You will need to start with a 4-Way harness and for this the Tekonsha T-One # 118467 will work perfectly. This custom harness will plug right into a factory port behind the driver's side trim panel for a completely "plug-and-play" installation. I have attached an installation video that you can even use for reference. Then once you have...
    view full answer...
  • Wiring Harness for 2020 Dodge Durango Without Factory Tow Package
    Yes, the Tekonsha T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector item # 118617 is a confirmed fit for your 2020 Dodge Durango without the factory towing package. The Tekonsha wiring harness plugs in line behind your Durango's rear tail lights to provide power and control over your trailers lighting functions. If you are in need of a 7-way vehicle connector than I recommend the Curt Trailer Connector Adapter - 4-Way to 7-Way RV and 4-Way Flat item # C57672. This adaptor...
    view full answer...
  • Solution for Adapter for Vehicle 4-Way to Trailer 7-Way
    It sounds like you're looking for an adapter like the Curt Trailer Connector Adapter - 4-Way to 7-Way RV and 4-Way Flat # C57672. The Curt adapter should be mounted to your vehicle. This will have both the 4-way and 7-way connection. Since it sounds like you don't need the 12V power or brake output you can leave the additional connections disconnected. All you will need to do is plug in your existing 4-way to the 4-way plug on the adapter. Once this is done, the 7-way connector will have...
    view full answer...
  • How To Install The Curt Echo On My 2013 Toyota Sienna With A 4-Flat Harness
    Since you already have the 4-flat harness installed on your 2013 Toyota Sienna, and have the adapter all you will need is The Wiring Kit for 2, 4, 6, and 8 Brake Electric Trailer Brake Controllers # 5506. I attached a review video link below.
    view full answer...
  • Factory Tow Package on a 2018 Mercedes GLC 300
    Yes, your 2018 Mercedes GLC 300 would have come with a functional 7-way if you have the factory tow package. The Curt Echo Wireless Trailer Brake Controller item # C51180 will work great in your Mercedes and you won't have to worry about running wires or permanently installing a brake controller.
    view full answer...
  • No Voltage Increase on Brake Output Pin When Brake Pedal Pressed
    The Curt # C51180 Echo wireless brake controller is a proportional brake controller. A proportional controller senses the rate at which the vehicle is braking, and will then send the proper amount of voltage to the trailer brakes so that the vehicle and trailer brake at the same rate. Unlike the older, time delayed style brake controllers, you will NOT get full voltage on the brake output pin unless the brakes are applied while the vehicle in motion. This being said, you shouldn't be...
    view full answer...
  • Curt 4 to 7 Way Adapter for the Curt Echo Wireless Brake Controller
    You assumed correctly. The Blue and Yellow pigtail leads on the Curt Adapter Item # C57672 do not have to be connected to use the Curt Echo item # C51180. You will just need to connect the 4-way to the adapter and then run the ground and power wires.
    view full answer...
  • Does the Alarm Always Sound in Reverse on the Curt Trailer Connector Adapter with Backup Alarm?
    Any time your vehicle is placed in reverse, whether you are towing or not, the alarm will sound on the Curt Trailer Connector Adapter with Backup Alarm item # C57102. To have the same connector without the beeping sound you will want the Curt Trailer Connector Adapter item # C57672. This is the same 7-way and 4-way connector without the alarm. I have linked an installation video below.
    view full answer...
  • Curt 4-Way to 7-Way RV and 4-Way Flat for 2016 Chevrolet Equinox
    I recommend the Curt Trailer Connector Adapter # C57672, 4-Way to 7-Way RV and 4-Way Flat. What I like about this is that it provides you the needed 7 way but extends out the existing 4 way making both available. Please note that while this will allow the 7 way to plug into vehicle it will still only support the lighting functions of the 4 way. If you want full functionality of the 7 way you will need the Universal Installation Kit for Trailer Brake Controller # ETBC7 as well. Please...
    view full answer...
  • Troubleshooting Left Turn Signal and Brake Light Not Working After 7-way Adapter Installation
    To answer your question, yes, it could be a bad ground. I would double check the ground from your 4-way as well as the ground for the 7-way adapter. Make sure they are securely attached to a clean, bare metal surface. You may even consider moving the ground from the recently installed adapter to a new position. The ground wire on the # C57672 should be secured directly to the frame. If that doesn't fix it, I would check all of the connections related to the left turn signal and make sure...
    view full answer...
  • How Do I Install A 7-Way Connector On My 2020 Subaru Outback
    In order to setup your 2020 Subaru Outback with a 7-way connector, you first will need to have a 4-way connector installed on your vehicle. You can do both with the Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires, part # ETBC7. It will involve some wire splicing, but when you are done you will have the 7-way and 4-way options on your 2020 Subaru Outback. I have included two product description links and video links below.
    view full answer...
  • Troubleshooting Overloaded Vehicle Harness On a 2015 Ford Transit T250
    That sounds correct to me. When you cut off the Curt T-Connector Vehicle Wiring Harness # C56327 converter box, it tried to pull all the power for the trailer circuits off the vehicle harness on your 2015 Ford Transit T250. It hopefully only damaged the fuses and not parts of the vehicle harness. Be sure to check the power wire that ran to the converter and see if the fuse was damaged or any of the harness is damaged as that would explain why it was not working when you recently tried to...
    view full answer...
  • Is Curt 4-Way to 7-Way Adapter C57672 Compatible with 4-Way C56452
    Yes the 4-way to 7-way part # C57672 is compatible with the 4-way kit part C56452 # C76CR that you referenced.
    view full answer...
  • Since The Curt C56407 Harness Already Has A Power Wire, DO I need To Run Another One For A 7 Way?
    The black power wire on the # C56407 is just for the powered converter as not all vehicles can handle the additional amperage draw of trailer taillights. This line will not provide the needed power for a battery or other accessory on your trailer, so you will need to run both. But on the plus side, already having the one line run will make running the second one for the # C57672 a lot easier. If you do not already have the wiring needed to do this, the Wiring Kit # 5506 will include all...
    view full answer...
    Image 1 for
  • 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...
    view full answer...
  • Replacing 7-Way Trailer Connector On a 1991 Chevrolet Suburban
    For your 1991 GMC Suburban V1500 we have the Curt T-Connector Vehicle Wiring Harness # C55312 4-way flat connector that will plug and play into the factory connections. As there is not a 7-way connector with the factory connections you can use the Curt Trailer Connector Adapter # C57672 to tie into the reverse light and charge line wiring wiring on the rear of your Suburban. You will be able to connect the 4-way harness directly to the adapter to take care of the running lights, turn...
    view full answer...
  • Do I Need to Run the Battery Wire When Installing 7 Way Connector to Use with Tekonsha Prodigy RF
    Because that connection is going to be relied upon to power the Tekonsha Prodigy RF # TK94FR, you will need to run power to the 7 way connector provided by the Curt # C57672 in order to use the Tekonsha Prodigy RF # TK94FR or any other externally mounted brake controller. It's important to run this line not only to provide power to the RF outside of the trailer battery, but this line will allow the 7 way to provide an auxiliary charge to your towed trailer's battery or a source of power...
    view full answer...

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