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Adapter 4-Pole to 7-Pole and 4-Pole

Adapter 4-Pole to 7-Pole and 4-Pole

Item # 37185
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Hopkins Wiring Adapters - 37185
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Adapter converts from 4 pole wiring on vehicle to 7-pole round plug and 4-pole flat. Additional wire leads for brake, power and accessory. Lowest Prices for the best trailer wiring from Hopkins. Adapter 4-Pole to 7-Pole and 4-Pole part number 37185 can be ordered online at or call 1-800-940-8924 for expert service.
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  • Reviews (532)
  • Q & A (0)
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Hopkins Trailer Wiring - 37185

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

Adapter converts from 4 pole wiring on vehicle to 7-pole round plug and 4-pole flat. Additional wire leads for brake, power and accessory.


  • Adapter converts from 4-pole wiring on your vehicle to 7-pole round plug and 4-pole flat wiring for trailer side
  • Adds additional wire leads for brakes, power, and accessory wiring
  • Wire functions:
    • White - ground
    • Blue - brake
    • Black - hot lead - 12 volt power supply
    • Purple - auxiliary
  • Mounting bracket included


  • Connector measures 3" x 3"
  • Distance between vehicle mounting holes: 2-3/16"
  • 90-Day limited warranty

product detail

Wire Functions:
White: Ground
Blue: Brake
Black: "Hot" Lead - 12V power supply
Purple: Aux. - Reverse Lights etc.

Note: If you run the hot lead (black wire), you will need a circuit breaker, for example 9510 (sold separately), between the adapter and the battery itself.

47185B Adapter 4-Pole to 7-Pole and 4-Pole - Hopkins # 47185B, TAP # 37185

California residents: click here

Customer Reviews

Adapter 4-Pole to 7-Pole and 4-Pole - 37185

Average Customer Rating:  4.8 out of 5 stars   (532 Customer Reviews)

Adapter converts from 4 pole wiring on vehicle to 7-pole round plug and 4-pole flat. Additional wire leads for brake, power and accessory.


Your information on how to connect to controller wasted a lot of time on the adapter under the steering column. In my Ford Expedition, the existing connector was plugged in and Brown not Gray. It was a simple swap. Instead, I tore apart panels under dash looking for an unconnected gray plug. Also you should sell the proper adapter for the rear end connector also. A simple plug swap vs. cutting 2 wires on Ford's wiring harness wires and using butt connectors would save so much time. Also, having a long purple wire for backup lights (not used very often) and short leads for hot and electric brakes was really stupid. I had to add 1 ft of wire to each - more butt connectors and potential for failure.

It is unusual that the 21 Ford Expedition will come with an adapter that is already plugged in under the dash to the left of the steering column. We do have listed as a tech tip for part # 37185
Adapter 4-Pole to 7-Pole and 4-Pole
that an additional length of wire may be necessary to connect the 7-Way socket of part 37185 to the vehicles tow package wires which are along the rear frame rail.
-- Etrailer Expert Jenny N - 02/28/2022


Really great, I needed this 7 pole to connect my High Camp teardrop to my 2014 BMW X3 and the 4 pole for a small utility trailer. They both work beautifully


The product itself is very well made. The 4-pin connector is molded into the product and very sturdy. The 7-pin connector is held closed by a spring and has a foam gasket to keep water out. The 4-pin wiring is only about a foot long, and the additional 7-pin wiring is a bit longer. I do not have a brake controller (but do borrow a trailer with the 7-pin wiring), so I removed those wires. I also hard-wired all the connections, so I can't speak to the quality of the 4-pin vehicle connector.

The mounting bracket is thin steel, which worked well for me, as I had to bend the mounting plate to make it work for my installation. The paint on the mounting plate appears to be high quality as I bent the plate and banged it around quite a bit during install and did not nick the paint. The plate is drilled so that is can be mounted with the 7-pin hinge facing up, down, left or right.

The hardware is zinc coated, so it should hold up well to the weather. I went ahead and replaced it with SS to make sure. I also replaced the standard nuts with SS nylon lock nuts to make sure nothing would back out due to vibration. If you plan on using the supplied hardware, I would strongly suggest Loctite on the mounting nuts.

I installed this on a CX-5 with hitch # 87623, wiring adapter # C56011 and hitch cover # I-728. Over all a very clean installation. The connector is completely hidden inside the bumper, but easily accessible.


This was exactly what I was looking for to add to my 2017 Ford Expedition! It is an easy to install plug-n-play product to convert a factory 4-pin connector to a 4/7-pin connector.

I plugged the 4-pin in, connected the brake wire, and grounded it. Ignoring the auxiliary + power cables, everything worked on the first test. The 4-pin connection was given some dielectric and wrapped with electrical tape to keep it sealed from the elements, and the slack was zip tied to secure it.

I still need to give it some finishing touches (fill the bracket gap with some black silicone, maybe find the reverse and/or power lines), but it lets me haul my camper!


2018 wrangler unlimited Sport S. Without trailer wiring. Completed installation today. Used a 4 flat along with a 7 pin converter. Works and fit perfectly. Very hot day and work slowly and carefully. Very satisfied . Great folks at etrailer. Great products, great quality and prices. I'm a several time repeat customer and couldn't be more satisfied.
4 pin harness Was a 56407 and the 7 pin adapter was a 37185.


It was pretty straight forward at installing and does what it’s need to do.

It is still working strong. When something works you don’t give it much thought.
Weston - 04/22/2022


AWESOME hitch unit. Strong, very easy to install (went in like a dream in 30 minutes), heavy duty, and right after I installed it on my 2011 Ford F-150 SuperCab I immediately towed a trailer with a 1971 MGB on it from North Carolina to Connecticut.

Awesome Hitch unit! Very strong and useful hitch unit. I dont even know it is on the truck until I need it. Wish I had purchased and installed this years ago, instead of trying to use the hitch ball installed on the bumper itself.
Jason M - 11/14/2021


Installed on a 2010 Ridgeline. Just what I needed at a great price. Install was a breeze. etrailer is the best place to find all the stuff that auto dealers rip you for. Good quality and the customer service is above reproach.


Installed on our 2019 Edge ST with no significant issues. Works as expected, has reasonable required depth behind connector for ease of install, and the bracket was quite adaptable after some bending and cutting. Not impressed with the overall feel, though - plastic seems lightweight and cover hinge pin is already rusting after two winter weeks in western PA. Long term durability tbd.


Just what I need to tow an RV trailer. Also has a four flat connector. Very easy to install on the 18136 bracket.


Nice quality adapter harness. I would highly recommend


Pretty easy to install and works as expected. The model in the video is a little different - the hole pattern is not quite the same. But the video was still useful.


I recently installed the 4-pole to 7-pole adapter on my 2015 Highlander. My first install worked OK, but I ran into a ground clearance issue using the original mounting location. Etrailer suggested using a 2 1/2" mounting box to relocated the connector. Part number 18156 worked perfectly.


Just what I needed!

It was working great until I destroyed it by getting stuck, because my Dodge Caravan sits so low. I fixed it by cutting out part of the plastic bumper and reinstalling the new one up higher.
Charlie - 04/25/2022


Wow after Charles great advice this was so simple to install, [online] video was point on and the hardest thing was finding the reverse wire.
Thanks so much for a good product and excellent advice, here is the pic after install!


Perfect install on my 2015 Thor Ace on a F53 Chassis. The F53 comes prewired but the coach builder only installed the 4 flat pin connector so I had to trace the four pin wiring up to chassis harness and found the blue (trailer brake) and light green/black (reverse lights) had been cut but there was enough wire on this harness to reach and connect. One note to anyone installing you will probably have to remove some electrical tap and flexible wire shielding to find the two chassis wires you need, but they are there and are probably located under the frame right by tow hitch.




The trailer wiring adapter was perfect and shipped in no time. Looks great on my ford ranger. Im very happy.
Was 4 flat only and now I can light my 7 way 18' trailer and have the capacity to add a brake controller (which I will add)


worked exactly for what i needed. I installed first on my 2010 expedition, then reinstalled it on my 2007 Chevrolet Silverado.

Great! still works great
Jeremy - 09/03/2021


First time buyer. Omg how great of a company. Everything u need and then some. Free shipping. And truth be told I had the pleasure of speaking with Terri N when I went to check out. 5 minutes into the phone call,I was thinking to myself what a wonderful person she is. Your company should feel very greatful to have someone like her working for u. I can not began to say it was the best buying experience I have had in a long time. Once again I want to say what a great place and Terri N what a wonderful person. Thank u again


Great product! Used to add trailer brakes to a 2003 Ford F150

It works perfect. No problems.
Wiring h - 08/30/2021


Ordered this 7-pin connector to connect to my pre-installed 4-pin connector (which was also purchased from etrailer last year) and this product has arrived on time, and as promised. Connection is very simple and the product is very light and not bulky, so it makes installation and appearance look professional done! VERY happy with this product and with the fast and friendly services of! Thank You!!

A year after purchasing the 7-pin connector, it still works as designed! I haven’t had any issues whatsoever and I am quite happy with the product. My main use for the 7-pin connector is to connect my 16’ Bass Buggy Pontoon boat and since day one it has served me right! Extremely pleased with the product and with!!
Stanville - 02/20/2021


2012 Chevrolet Express..Looks and works great! Easy install..2 1/8" hole saw for center, 3/16" drill bit for mounting screws. Thank you etrailer!


This item was received without instructions. The 4pin is easy enough to plug into any other 4 pin. Once you ground the white lead the brakes and signals work well. I dont know what the blue or purple wires are for, as instructions did not come with this item- wiring diagram either. Black lead I assume is power, to be connected to a hot lead, for internal trailer lights, idk.
Otherwise, I am happy.

The black wire is the power wire it needs to be connected to the positive side of the battery by using a 40 amp circuit breaker. If you are using your reverse trailer lights attach the purple wire coming out of the 7-way connector to the your reverse light wire. The blue wire is for electric brakes its going to go to the output wire on your brake controller. There should be a black wire coming from your brake controller that will connect to the positive side of the battery as well using a 20 or 30 amp circuit breaker. The red wire from the brake controller will connect to the cold side of the brake switch above the brake pedal. The white wire on the brake controller grounds to the negative side of the battery. I have attached help articles to assist you.
-- Etrailer Expert Heather A - 07/10/2018


I bought this so I can convert my dad's trailer to pull I only had a four and I needed a seven so I went and used a four to make it a seven. It's a very nice product it's got nice rubber grommets to keep everything protected.

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