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Custer Trailer Connector Adapter - 4-Way Flat to 7-Way Round

Custer Trailer Connector Adapter - 4-Way Flat to 7-Way Round

Item # KIT-7P-4
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Convert a 4-way flat trailer connector to a 7-way round connector with this adapter. The pigtail harness hardwires into your vehicle's existing wiring. Built-in ABS plastic cover protects the 7-way terminal from dust and moisture. Lowest Prices for the best trailer wiring from Custer. Custer Trailer Connector Adapter - 4-Way Flat to 7-Way Round part number KIT-7P-4 can be ordered online at or call 1-800-940-8924 for expert service.
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Custer Trailer Wiring - KIT-7P-4

  • Wiring Adapters
  • Single-Function Adapter
  • 7 Round - Round
  • Plug and Lead
  • 0 - 5 Feet Long
  • 4 Flat
  • Custer

Convert a 4-way flat trailer connector to a 7-way round connector with this adapter. The pigtail harness hardwires into your vehicle's existing wiring. Built-in ABS plastic cover protects the 7-way terminal from dust and moisture.


  • Adapter converts your vehicle's 4-way flat trailer connector to a 7-way round connector
  • Pigtail harness hardwires to existing wiring for brakes, power, and accessory
  • Built-in cover protects the 7-way end from dirt and moisture when not in use
    • Hinged cover opens 180 degrees for effortless connection
  • Pull grips make 7-way plug easy to install and remove
  • ABS plastic construction is strong and durable
  • Flexible wire between plugs provides wide range of motion
  • Length: 18"

KIT-7P-4 Custer Prewired Trailer Connector Adapter w/ Dust Cover - 4-Way Flat to 7-Way Round

Video of Custer Trailer Connector Adapter - 4-Way Flat to 7-Way Round

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

Video Transcript for Review of Custer Wiring - 4-Way Flat to 7-Way Round Wiring Adapters - KIT-7P-4

Hi there, I'm Michael with Today, we're going to take a quick look at this Custer 4-Way Flat to 7-Way Round Trailer Connector Adapter. This is going to convert your vehicle's 4-way flat trailer connector to your trailer's 7-way round connector. So it's going to convert that so that your trailer will be compatible with your vehicle wiring. This will hard wire to the existing wiring for your breaks, power and accessories. So your white wire is going to be your ground, your black is going to be your reverse lights and blue is going to be your electric brakes.

The yellow, thick wire here is most likely for your auxiliary power but you will of course, want to check all those connections, make sure the wiring matches up with your trailer and your system so that everything is going to be lined up properly. If you do need to make any adjustments, the back side of our plug here does have this rubberized cover that you can pull back and just with a small Phillips head screwdriver you can undo those connections, move them around, if needed and then just slip that cover back in place, to protect those connections from any dirt, debris or moisture getting there. On the front side, our built-in cover is going to protect our 7-way connection from dirt and moisture. It's a nice, solid metal construction so it's going to be very strong and durable. It's got this hinged cover that opens 180 degrees so that we can easily get our plug put in there and make that connection.

As far as getting this installed, the wiring is going to be pretty easy, just plugging in our 4-pole to our vehicle's wiring and then plugging in our 7-pole on this end. We do have about 18 inches of flexible wire that's going to provide a nice wide range of motion so that we can get this hooked up where we need to. One thing I will say is, if you are thinking about installing this permanently, the biggest challenge will probably be mounting your 7-way end so it's got these two mounting holes that you could just drill holes into the body of your vehicle and get that mounted in place, if you want. When I installed the similar option, like this, on my wife's vehicle, a few months ago, I used a system like you see on the screen there, so the Hopkins Universal Mounting Bracket would install right behind this so use those two holes and then get that connected in place and then, on top of that, I would use the Tow Ready No-Drill Mount Bracket so that will create a kind of clamp, a hose clamp around your trailer hitch so that it will then stick out and then you can put that Hopkins Universal Mounting Bracket on the front there and then just put this through and get it connected in place so that it's going to be sticking out from your hitch and give you a nice solid location to mount this to. Just something that I would recommend, personally, that's kinda how I did it when I installed a similar option on my wife's vehicle, just so that you have a nice solid place to get this mounted.

You don't have to worry about hurting your vehicle's body. Overall, I think that this is going to be a really nice option, very easy to get installed, convert your 4-way flat plug to work with that 7 round on your trailer so that you can pull your trailer with you vehicle. That's going to complete our look for today. Again, I'm Michael with Thanks for watching..

Customer Reviews

Custer Trailer Connector Adapter - 4-Way Flat to 7-Way Round - KIT-7P-4

Average Customer Rating:  5.0 out of 5 stars   (2 Customer Reviews)

Convert a 4-way flat trailer connector to a 7-way round connector with this adapter. The pigtail harness hardwires into your vehicle's existing wiring. Built-in ABS plastic cover protects the 7-way terminal from dust and moisture.


Thank you so much for taking the time to help me. I've been driving my trailer for a month. You're company was the only one who could help me find a converter for my classic trailer. Thank you again


the product was a pig tail wire to convert a 4 pin trailer plug to a 7 pin. it far exceeded my expectations and took a load off of my mind about wiring my new pickup.


Ask the Experts about this Custer Trailer Wiring

  • Adapter for 4-Flat on Vehicle to Attach to 7-Way Round on Trailer
    Thank you for the photos they were very helpful. What you have on your vehicle is a 4-way flat, and on your trailer you have a 7-way round, which is less common than a 7-way blade-style, but there is still an option for you to connect the two. The correct part adapter for this is the Custer Trailer Connector Adapter - 4-Way Flat to 7-Way Round # KIT-7P-4. If you just want to use it for your the same functions as your 4-way - the turn signals and tail lights - you only need to plug your...
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    Image 1 for Image 2 for
  • Adapter to Connect 4-Way on Vehicle to 7-Round on Trailer
    We have exactly what you need, an adapter that converts your vehicle's 4-way flat to a 7-way round connector, which is the following: - Custer Trailer Connector Adapter - 4-Way Flat to 7-Way Round # KIT-7P-4 This is the same as the part number you mentioned, but with a 7-round as opposed to the 7-blade so it'll be perfect for your needs, giving you the functionality of your vehicle's 4-way while connected to your trailer's 7-way.
    view full answer...
  • Using Adapter # C57674 to Tow 7-Way-Equipped Camper Trailer with 4-way-Equipped Vehicle
    The 2004 Toyota Sequoia has a rated towing capacity of either 6200-lbs or 6500-lbs depending on the version, so you should be fine in terms of towing capacity for your Shamrock 19-foot pop up which weighs either 3524-lbs (model 19) or 4432-lbs (model 19L). You will also need to verify that your 2-inch hitch receiver is rated adequately for your trailer load; there should be a safety/warning sticker on it to indicate its capacity. The Curt Trailer Connector Adapter # C57674 that you referenced...
    view full answer...
  • Is There a 4 Round to 7 Round Adapter
    We have a possible solution for you but there is no such thing as a 4-round to 7-round adapter; you would need to make your own. What you could do is use the Custer Trailer Connector Adapter - 4-Way Flat to 7-Way Round # KIT-7P-4, cut off the 4-way flat and wire in the RoadMaster 4-Wire Connector # RM-910030-2.
    view full answer...
  • Availability Of Short 4-way to 7-way Adapter
    The closest thing we have to a molded 4-way flat to 7-way blade adapter is the Custer Trailer Connector Adapter - 4-Way Flat to 7-Way Round # KIT-7P-4 which has the 4-way connector to plug into the 4-way on your vehicle and give you the 7-way blade connector you are looking for. If you are just needing the lighting functions of the 7-way then you will not need to use the 3 additional wires. If your trailer has trailer brakes, or has a battery and you need 12v power in the connector you...
    view full answer...
  • 2015 Ford Transit T-350 Van Trailer Connector not Working What Should I check
    From what I understand your 2015 Ford Trasit T-350 has a connector on the back for use with trailers that looks similar to the Custer Trailer Connector part # KIT-7P-4 and you have added an adapter similar to 7-Way Round Pin to 4-Flat Adapter part # 118709 to plug your 4-way flat trailer plug into and you are getting no power to the lights at all. This sounds like a pretty common issue we run into often. That being the ground wire. This could have been damaged or has corroded at the connection...
    view full answer...
  • Adapter to Go From Tow Vehicle 4-Way to Trailer 7-Way
    To go from the 4-way of your tow vehicle to the 7-way of your trailer you'd the 4-way round connector part # KIT-7P-4 with the 7-way socket # HM48480 and you'd need to wire them together.
    view full answer...
  • 7 Pole Mounting Bracket For A Draw-Tite Hitch On A 2019 Subaru Crosstrek
    For your 2019 Subaru Crosstrek, the mounting bracket you would need to mount a 7 pole plug on a draw-tite hitch with integrated mounting points is the Mounting Bracket and Installation Hardware - Pollak 7-Pole, RV-Style Trailer Connector - Vehicle End Item # PK12711U. This bracket comes with the hardware not only to mount the bracket but also to mount the plug to the bracket. If you are looking for wiring as well and are wanting to add a brake controller I recommend the following items: T-One...
    view full answer...

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Info for this part was:

Employee Jameson C
Expert Research:
Jameson C
Employee Adam R
Expert Research:
Adam R
Employee Rachelle B
Written by:
Rachelle B
Employee Wilson B
Updated by:
Wilson B
Employee Brian T
Updated by:
Brian T
Employee Michael B
Installed by:
Michael B

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