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

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

Item # 37185
Our Price: $65.26
Trailer Wiring
Shipping Weight: 0.94 lbs
In Stock
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. Great 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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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 Satisfaction Score:

Customer Reviews

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

Average Customer Rating:  4.8 out of 5 stars   (597 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.


Really nice trailer wiring adapter. Very easy install. Takes about 30 minutes with all the tools needed. Drill, 7/64 bit for pilot holes to mount the bracket, flat blade screwdriver and 11/32 nut driver and two #10 self tapping metal screws with locking split washers and a couple zip ties to tidy up the wiring harness.


This company is amazing as they offer an incredible vast inventory of most anything one can imagine relating to trailers. They sent a nice email confirming the order and notice of being shipped, which arrived in just three days.


Worked great in tandem with a new wiring harness. Still working after a year of use.


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 like always from etrailer, the right product, right on time, and right on the money.


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.


Used on my wifes van and works great with our camper. Only complaint is wish is had a way to stabelize to the vehicle a bit better two screws at the top are all that hold it on to the van.

I recommend using part # 18140
No-Drill Mount for Electrical Mounting Bracket - Short
which will zip tie to the hitch. Then you can attach the harness bracket to the end of this bracket.
-- Etrailer Expert Jenny N - 03/02/2023


I had a great experience. Got the product with no problems.


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.


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)


Thank you so much! You all are so attentive and helpful!


Jessica M is the best , very pleasing and helpful . I will always ask for her e trailer products are always QUALITY


Perfect fit. The wire leads were long enough to connect to the oem harness


The personal service Steve provided was great. He went above what I expected and answered all my questions. He asked all the right questions and verified this part was correct for the brake controlled I had. He went step by step over the correct wiring to ensure I maintained all the functionality of my current system.


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


Working fine one year after being installed! Towing a Bushwhacker, I had to draw a wire to the battery for operating the camper electric brakes, and added a Curt Echo bluetooth brake controller.


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


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!


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.


I use these adapters to install 7-way connectors on trucks that have no factory trailer wiring provisions.


Fast shipping, easy fit, good customer service


Great product and description. Installation was very easy and smooth. Everything lined up, the installation video was on point


They shipped my harness immediately to UPS. After two weeks I did not receive it, so I called the guy said it would be there Friday or Saturday, Saturday was the fourth so I knew that was gonna happen. So I waited till Thursday and called and talked to Amy E., She was great, she Found out that my harness was sent back to them. Amy re-ordered my harness, I received it on Saturday! The harness fit perfectly! So I am going to give them an excellent review! My patients was worth wait ,because it was exactly what I needed! Thank you so much Amy I appreciate all the help.

Show More Reviews

See what our Experts say about this Hopkins Trailer Wiring

  • Trailer Connector Adapter To Convert 4-Pole on Vehicle to Tow 7-Way Equipped Trailer
    We do indeed have an adapter that would work for you, the part # 37185 you referenced. This adapter would plug into the 4-pole on your truck. There are four loose wires as well, but if you don't need the 12-volt power or brake output circuit active, you'll just need to ground the white wire to the truck frame. You can bundle up the remaining wires and tuck them up out of the way. The adapter will also provide you a functioning 4-pole. To see a product demonstration video featuring the...
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  • Installation Of 4-Pole to 7-Pole On 2006 Ford Expedition
    I recommend using the Hopkins Adapter 4-Pole to 7-Pole and 4-Pole, part # 37185 for your 2006 Ford Expedition. I have attached a photo of the adapter that shows the wires and what they are used for you can check out. You can find the wires you need to connect the adapter to on the driver's side frame rail as shown in the photos I have attached. I have also attached a helpful article that explains how to complete the installation. I recommend using a circuit tester like part # 3808 to...
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  • Adapter to Convert Vehicle 4-Pole Vehicle Connector to 7-Way Trailer Connector
    You can use Hopkins 4 Pole to 7 Pole Adapter # 37185 to mate your 4-pole equipped vehicle to your 7-way equipped trailer. The extra wire leads do not have to be connected for your no-brakes application but you will have them in the event that you ever want to install a trailer brake controller or have 12-volt power available for use with another trailer.
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  • Trailer Adapter to Convert 4-Pole Flat to 7-Way RV-Style Blade Connector
    You found the correct adapter to convert your F-150's 4-pole flat trailer connector to a combination 4-pole and 7-pole to allow you to tow two types of trailers with different wiring connectors. Your existing 4-pole will simply plug in to the female connector on the Hopkins # 37185. The included mounting bracket and hardware will allow you to install this where you prefer. If you ever want to add a trailer brake controller for use with trailers that have electric brakes the extra wire...
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  • Trailer Wiring Circuit Suggestion for Powering Back Up Camera Mounted on Trailer
    You could use the running light circuit for the trailer. That way whenever you need to activate the camera system you could flip the running lights or head lights on.
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  • Should Two Batteries of Different Age be Wired in Parallel
    It's not recommended to use an old depleted battery with a new one when wiring them in parallel. That is because Ohm's Law tells us that the stronger battery will discharge through the weaker battery - you will always have current flowing, wasted current that does nothing but warm batteries. And as this happens, there will be battery discharge.
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  • What To Do with Extra Wires of Adapter 37185 that are For Unused Circuits
    You are correct. The unused wires of the # 37185 can be taped up and out of the way since you have no use for them.
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  • Parallel Batteries Versus Batteries Wired in Series
    If two batteries are wired in parallel, the positive terminals of each battery will be connected together, as will the negative terminals. Assuming both batteries are 12 volt, you'll have a 12 volt output but there will be more capacity. If the batteries are wired in series, the positive terminal of one battery will be connected to the negative terminal of the other. This would double the output of the batteries, assuming each battery is a 12 volt, wiring the batteries in series would...
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  • How Does Brake Output Circuit of Brake Controller Get Connected to a 2005 Pontiac Vibe with 7-Way
    Since your 2005 Pontiac Vibe would not have came from the factory with a 7-way the one you have would be an aftermarket one. To connect to the blue wire of the connector will require you to run a 10 gauge wire back from the blue wire of the controller to the blue wire of the 7-way which would be the pin in the 5:00 position of the connector. I attached an install video that shows a brake controller and 7-way being installed in a similar 2003 Pontiac Vibe as yours for you to check out to...
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  • Bolt Doesn't Want to Thread to Install 7-Way Bracket On a 2011 Nissan Pathfinder
    It sounds like the existing weldnut on your factory hitch has gotten corroded over time and that is why the 8 mm bolt will not thread into it. This is a very common problem on vehicles that have seen a couple winters or more. I attached the video you referenced and at the 1:47 mark of it our installer shows how to install the bracket. I also attached a couple articles on cleaning weldnuts for you to check out as well.
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  • 7-Way Recommendation for a 2009 Ford Escape
    It sounds like you are referring to a 7-way trailer connector as that style of connector has a flap that covers the opening of the connector when not in use and is very common on trucks. To convert your 4-way to a 7-way all you would need part # 37185.
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  • 7-Way Recommendation for a 1999 Ford Expedition
    If your trailer does not have brakes all you would need is the part # 37185 as an adapter to convert the 4-way to a 7-way.
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  • 4-Way to 7-Way Adapter Recommendation for a 2007 Honda Pilot
    To connect the 4-way of your 2007 Honda Pilot to the 7-way of your trailer that does not have brakes all you would need is the adapter part # 37185. The 4-way of the Pilot will plug into it and the 7-way of your trailer will plug into the other end.
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  • Running Light Circuit Not Working on 4- to 7-Way Adapter # 37185
    On the Hopkins 4- to 7-Way adapter # 37185 the brown wire is the running light circuit. There could be a break or a problem with the connection on that brown wire somewhere between its 4-Way and the back of the 7-Way. Also make sure that the white ground wire on the adapter is attached to a clean and corrosion free bare metal surface. This wire must have a good connection or you could run into problems with some of the lights. A weak ground could be the result of this issue since the running...
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  • Switching Trailer from 7-Way to 4-Way and Right Turn Signal Does Not Work
    On a 7-Way blade style trailer connector the brake lights and turn signals are on the same circuits. So you will have one for left turn and brake lights and another for right turn and brake lights. If the brake lights are working on the right side then the turn signal should also be working. If it isn't then there is likely a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like...
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  • Installation of Electronic Brake Controller on 2010 Ford F-150 w/ Factory 4-Way
    To install a brake controller on your 2010 Ford F-150 w/ factory tow package and 4-way connector, you will need to install Adapter 4 Pole to 7 Pole, part # 37185. You will need to run 2 wires, to the front of the truck, the Black wire for 12 volt power, and the Blue wire, which supplies power to the brakes. The Blue and Black wire will connect to the Ford wires that terminate along the frame of the F-150 near the spare tire (see FAQ). Then, you will need to use the vehicle specific adapter...
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  • Adding a 7-Way Trailer Connector to a 2012 Jeep Wrangler for Lights Only
    If you only need lights to work on your trailer then you can use # 37185 that you have referenced. You will plug in the 4-Way you have to this adapter. Then you will need to ground the white wire to the vehicle frame. The other wires can be taped up and stowed out of the way except the purple wire. That one will need to connect to the reverse light wire behind the tail light on the Jeep. If you do end up wiring the remaining wires in later, the black wire is for 12 volt power and the blue...
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  • Where is the Red and Blue Wires on a 1994 Ford F-150 for Installing a 4-Way to 7-Way Adapter
    The connector you are looking for that has the red and blue wires is in the driver side frame rail near the rear of the vehicle. Check out the video I attached that shows where it is at right around the 2 minute mark. I also attached a picture of what the connector will look like.
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  • Does the White Wire on the 4 to 7-Way Adapter # 37185 Have to Be Connected on a 2012 Mazda CX-9
    You will need to ground the adapter # 37185 to the vehicle frame for it to work. The other functions if you do not need them can be taped up and stowed out of the way. The 4-Way that you installed may be ground but that ground does not continue on the 4-Way part of # 37185. That is why the white ground wire must be attached.
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    There are two ways to get your trailer lights working on your 2008 Jeep Grand Cherokee. The first way is as you thought - take the vehicle back to the Jeep dealer and have them activate (reprogram) the internal Jeep computer to activate the tow package wiring. An alternative choice is re-wiring your vehicle with the Universal Installation Kit # ETCB7 and T-One Vehicle Harness # 118425 by Tow Ready. I have attached an install video of this harness on a 2008 Jeep Grand Cherokee and also...
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    The way you are describing the trailer connectors on the vehicle it does not sound like a factory connector. But regardless of if it is factory or aftermarket, check to make sure there is not a loose white ground wire not connected to anything. The harness will not function fully without a proper ground. It is possible that the lights on the trailer are over drawing the ability of the trailer wiring on the 2012 Dodge Grand Caravan. If it is factory wiring then you would need to consult...
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  • Troubleshooting Trailer Wiring Issue with 2008 Jeep Liberty
    The fact that your trailer lights seem to work just fine until the vehicle headlights are switched on indicates a ground problem somewhere in the system. The quick way to confirm a ground problem would be to disconnect your existing ground connection from the trailer and use a butt connector to temporarily connect a length of wire long enough to reach the negative battery terminal. If this temporary jumper fixes the problem (which it most likely will), you have confirmed a poor ground...
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  • Troubleshooting a 12 volt Power Circuit on a 2006 Ford E350 Van
    It sounds like a fuse has blown somewhere on that circuit, but since you checked that already you might try checking the back of the 7-way to see if the circuit is connected to the connector properly. There could be corrosion there that is causing the circuit to short out. You might use a circuit tester like our part # 3808 to check for voltage behind the connector and then work your way up the circuit looking for voltage to see where the problem lies and fix as necessary. Since you said...
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  • Where is the Brake Controller Plug for a 1998 Ford F-250 Heavy Duty
    On a 1998 Ford F-150 that came with either a factory 7-Way or 4-Way, the factory harness to plug in a brake controller should be located under the dash, near the center console. It could also be a little behind the center console. I have included a link to a video and a link to an FAQ article that will help you.
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