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Adapter 7-Pole to 4-Pole and 5-Pole

Adapter 7-Pole to 4-Pole and 5-Pole

Item # 37385
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Trailer Wiring
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Adapter 7-Pole to 4-Pole and 5-Pole Multi-Function Adapter 37385
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Lowest Prices for the best trailer wiring from Hopkins. Adapter 7-Pole to 4-Pole and 5-Pole part number 37385 can be ordered online at or call 1-833-496-1390 for expert service.
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Hopkins Trailer Wiring - 37385

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


  • Wiring Adapter - converts the 7-way trailer connector on the vehicle to a 4-way or 5-way connector to match the trailer

If your truck has the connector on the left, and your trailer has one of the connectors on the right, you will want this adapter.
30300 18004
Vehicle End Trailer Ends

47385 Adapter 7 Pole to 4 Pole and 5 Pole - TAP # 37385

California residents: click here

Video of Adapter 7-Pole to 4-Pole and 5-Pole

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

Video Transcript for Hopkins Wiring - Wiring Adapters - 37385 Review

Today we're going to review part number 37385. This is the Hopkins 7-pole to 4-pole and 5-pole adapter. This is a wiring adapter that will convert the 7-way trailer connector on your vehicle to either a 4-way or a 5-way connector to match the trailer. As you can see the dust covers are included to protect them if you're not using the connector. Basically you'll notice when you plug this into the 7-way it'll give you your lighting functions on the 4-way. It has the ground, it gives you your tail light function, your left turn and brake, and your right turn and brake. On the 5-way, when you plug that in it will give you all the same functions of the 4-way but the extra one is for the reverse light circuit.

Lots of times on a boat trailer will use a 5-way so you'll be able to use that reverse light circuit for the surge actuator on the trailer itself. That should do it for the review on part number 37385, the Hopkins 7-pole to 4-pole and 5-pole adapter. .

Customer Satisfaction Score:

Customer Reviews

Adapter 7-Pole to 4-Pole and 5-Pole - 37385

Average Customer Rating:  4.8 out of 5 stars   (105 Customer Reviews)


Junk. Did not work new out of the box

You mentioned that it did not work as new out of the box and I wanted to see if you could explain in more detail what happened.
-- Etrailer Expert Jenny N - 11/08/2022
I opened it new out of the box, plugged it into my trailer and vehicle and got no lights, plugged a different adapter in and instantly had trailer lights. The plug did not work brand new out of the package its first use. hope this clarifies ,
-- comment by: John - 11/08/2022
It does, thank for answering. I can send warranty information to you if you would like to have it replaced.
-- Etrailer Expert Jenny N - 11/08/2022


This was my second order. Great service! You have the hard to find parts and expeditiously ship them. I will highly recommend etrailer to others.


Workedcjust fine.


In my quest for a 7 pin to 4 pin connector to operate lights on my luggage rack my search led me to etrailer. Initially I spoke with Derek who was very helpful and sent me a connector that was 7 to 5 pin as that's what I thought I had. Turns out I was wrong so I called back to order a 7 to 4. This time I found Ashley and she quickly mailed me the 7 to 4.
These two employees were most helpful and very courteous in my dealings with them I'm happy to recommend etrailer for these kinds of products. Give them a try!

Works fine. Only used it a few times but no problems.
Jim L - 07/29/2018


These plugs work great. I use it for my boat trailer (5 Plug), Jetski trailer (4 Plug) and a Car Hauler Trailer (7-way). Very simple to use. Highly recommend it you use multiple trailers with different plugs and braking systems.

Everything is still working great with no issues!!
Ted - 09/10/2020


Needed one


Product was delivered in a timely fashion and matched the part ordered. Quality was excellent and provided the features per price point that was desired. So far, no problems in use. It is now part of my basic trailering kit. Other products are available that have more features but they are larger and cost more. For my use this is right on. Product support and useful information from etrailer is consistently excellent.

After one year the wiring adapter continues to work well. I would not change my original review.
Capt.Wanabe - 07/23/2018


Provides a quick and simple solution for connecting a trailer with a flat-4 or flat-5 plug to my truck with its round 7-way plug.

We recently towed a rental trailer from Maryland to New Mexico. This connector worked perfectly!
Robin N - 07/21/2017


The adapter fit tightly and worked well. Be careful attaching and detaching the trailer harness so, you don't bend the bottom metal, male connector.

Everything installed correctly the first time and worked on my 2011 Honda Pilot. What a relief. It took me about 2.5 hrs because, I had to figure out fasteners for the bumper, existing wiring harness, etc. so I didn't break anything. Make sure you have a center punch, sharp metal drill bits and oil to pilot holes for self tapping screws. I am very happy with the harness and adapter.


Nice quality. Convenient all in one ada pter.


Was exited when I found this on etrailer's website...I have 2 different trailers with 2 differents light harness connectors. This works need to switch out or have two or more adaptors in truck!! Highly recommend!


Exact replacement for the one I lost, had no problem finding it at etrailer since I had previously bought hard to find parts I needed when replacing worn parts on my boat trailer. Thanks etrailer.

Working great, I am causious about not losing it again, thanks again.
Jimmy - 04/07/2019


Overall...much better than going through the dealership for the sake of time and money. The online videos hit all they key points and steps bit there was some mechanical ingenuity required on my part. Mounting the bracket was the most challenging part to install and it was correctly represented in other reviews.

Personally, I wanted the 7 pin connector flush to the bumper and had to bend the mounting bracket and cut out the plastic bumper to get a tight fit. Looking back however, I think that if I would have cut out just enough of the bumper to accommodate the angle of the mounting bracket (when attached to the frame) then I would have still achieved both a solid connection and clean, professional look.

All in all, I'm very satisfied with the product and instructions received from e Trailer and staff.


It was great and worked exactly as it was supposed to until my dog pulled it out of the receptacle and chewed it to bits.
I put an external tire carrier on my car and was using the three hole side to power my relocated license plate.
The rig lasted through all sorts of weather and terrain like a champ. I got about 9 months out of it before it was devoured. I'm sure it would have lasted for years if not for the >-< dog.


This adapter works perfect. It easily installs into the round 7 pin connector. The connector worked as all lights were lit and I was able to back my boat trailer into position with no problems. The 5 flat is used for the inclusion of the surge brakes on my boat trailer. I would recommend this to anyone needing the conversion adapter.


As always, product arrived quickly and well-packed. Good quality and is working well on my vehicle. etrailer can be counted on for quality and customer service.

No problems, never give it a second thought. Can depend on it to do the job.
David - 03/28/2020


This trailer light adapter allows me to haul 2 different trailer with one vehicle. Delivery was in 3 days and I also purchased a 5 wire trailer wiring harness to match


Good product. Works well and is very convenient to have both 4 and 5 pin connectors. Only issue is dust cover on 5 pin sticks to ground pin when you pull it off with the tab and can bend the ground pin.


Just what I needed, have a boat and two wheel trailer with different plugs , ordered the weather tech mud flats also for my 2011 gmc 1500, they were easy to install and look great, all items where to me in three days. Great job etrailer


Fits the round plug on the vehicle perfectly. Haven't hooked it up to the flat wire yet, but assume it should be fine. Getting this adapter with the covers for the 4 & 5 flat is absolutely the right way to go. I'm towing a 5500 lb boat with surge brakes.
Jesse did an outstanding job of helping me.


The wiring kit fits perfectly. I had a small problem with the operation of the brakes on my trailer but a quick call to the great service department and my problem was quickly rectified. I will do business again.


I find this adaptor to be very useful as I own and frequently tow, different size trailers all with different plug connectors. Nothing is worse than not having the right connection to make your trailer connection.


The Adapter made a quick and easy connection between my truck and the trailer. All lights functioned properly.

Great adapter at a great price.


Fantastic. Elliminates need for 2 separate harnesses. Many trucks already have a 7 pole connector and a 4 pole connector but nobody has a 5 pole connector so this kills 3 birds with one plug.


No interaction with George, I ordered online. However the girl who answered the phone was clueless, i had to find these parts on my own.

etrailer needs to hire knowledgeable sales people if they hope to stay on top.

Show More Reviews

See what our Experts say about this Hopkins Trailer Wiring

  • Left Side Trailer Stop/Turn Signal Lights Not Working
    If there are no brake/turn signal lights on the left hand side of your trailer then the first thing you will want to do is check the fuse for that circuit in your vehicle's fuse box. It should tell you in the owner's manual where that fuse is located but if not it will be labeled on the underside of the cover/lid. After the fuse is checked you will then need to test the left hand brake/turn signal circuit on the vehicle side trailer connector. If no power is present then there is most likely...
    view full answer...
  • Trailer Lights on Rental Trailer Cut Out Once Vehicle Headlights are Switched On
    What you mention is a classic system of a ground problem. Everything works fine until the running light circuit is activated, at which point the trailer's taillights are drawing maximum amperage. If there's a ground problem, this is where it's going to show up. On the vehicle side, make sure the white ground wire is securely attached to clean metal on the vehicle frame or chassis, but the chances are that the ground problem is somewhere in the wiring on the trailer itself. The main ground...
    view full answer...
  • No Turn or Brake Signals While Towing With 2018 Ford F-150 After New 7-Way Installation
    When you say receiver I believe you mean a trailer wiring connector. The trailer connector does need to be grounded to a clean bare metal surface of the truck's frame which is most likely causing the issues with the lights. Another thing to check for is any corrosion on the pins or bent pins of the trailer connector which may be causing a bad connection. If there is corrosion you can lightly sand it off but it sounds like you have a classic ground issue especially since you said the trailer...
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  • Troubleshooting Brake Lights Blowing Fuse When Connected to Trailer
    Based on your LED tester results and the fact that the trailer works fine with another vehicle we at least know that the issue is somewhere on the tow vehicle. If you can tell me what model vehicle you have along with the type of trailer harness that was installed (or if it's factory) I should be able to offer some more specific troubleshooting steps but in the meantime I first recommend inspecting the connector itself at the rear bumper. Check for any corrosion or debris that might be...
    view full answer...
  • Troubleshooting No Brake Lights/Turns Signals on Trailer Wiring
    Sounds like you've eliminated the problem to being on the trailer side of your towing setup since all of the pins of your trailer connector are testing good. Typically the issue with no brake lights/turn signals is related to an insufficient ground for either the trailer wiring as a whole or the main ground assembly of the wiring. Since both brake lights and turn signals aren't working I'd assume it's a weak ground for the trailer overall. To fix that you'd just need to make sure the...
    view full answer...
  • Can Both Connections of Adapter # 37385 be Used for Tow Dolly Lights and Magnetic Lights?
    Yes, you can use Adapter # 37385 for both of your 4-way connections; there will simply be an unused pin in the adapter. However, you will need to be sure that the amperage draw from both lights does not exceed the rating of the tow package wiring on your RV. Your other option would be to simply cut off the 4-way on the magnetic kit and splice it into your tow dolly's wiring. I've added a pair of links to video reviews of this part for you to take a look at.
    view full answer...
  • Adapter from Vehicle 7-Way to Two 4-Way Flat Connectors
    We actually do have an adapter that will accomplish just what you're needing! The Hopkins Adapter # 37385 goes from a 7-Way to a 4-Way and 5-Way combination. I reached out to my contact at Hopkins who said you can use both of those connections at the same time. All you need to do is plug one of the connectors to the 4-Way and then simply line up the ground pins on your 2nd 4-Way and the 5-Way for this to work. The ground pin is the one that is different from the rest.
    view full answer...
  • Troubleshooting Brake Lights and Running Lights Not Working On Trailer at Same Time
    Try improving the connection of the main ground wire of the trailer wiring harness. Make sure it is attached to a clean metal surface. Or you can run all of the trailer wires back to the main ground. This is actually the ideal solution. But you can also check the current grounds for the lights to make sure they are making a solid connection to a clean metal surface. What you described is the classic insufficient ground scenario so finding a way to improve the grounds will fix the problem.
    view full answer...
  • Troubleshooting Trailer Blinkers that Both Blink at the Same Time
    You have a short between the stop/turn circuits of your trailer wiring. Normally the blinker/stop circuit for each side of the trailer goes to either side of the trailer separately but in your situation the two wires most likely have exposed wire between them which is allowing the voltage from either side to transfer to the other as well. You'll need to go over the wiring of the trailer to track down the short and fix as needed.
    view full answer...
  • Tail Lights On Dump Trailer Only Work With Bed Down
    It sounds like your tail lights might be located on the bed of the trailer rather than the frame and they are then losing the ground contact when the bed is down. In order to try and resolve this issue I recommend running a ground wire from each tail light up to the main trailer ground. That should fix your issue but if it does not then please just let me know and we can then go from there.
    view full answer...
  • Is It Normal For Relays For Brake Lights To Be Warm
    I'm glad to hear you found our answer page helpful! On you 2011 Volvo VNL it is normal for relays to be warm when it is on, but not be too hot to touch. If your relay is too hot to touch there is a few issue that could be going on. The relay may have an internal short that is allowing it to get hot which would require you to replace the relay in question. There may be a short in the circuit feeding the relay causing excess heat which would require you to follow the wire coming from...
    view full answer...
  • Troubleshooting Trailer Brake Lights that Go Out When Headlights are On
    There are two sets of grounds you need to check. The grounds for the taillight assemblies and the main ground for the trailer that runs from the trailer connector to the frame of the trailer. Between one of those grounds lies your problem as what your are describing is a textbook example of an insufficient ground. Another possible solution (although unlikely) is that you are overdrawing your trailer light circuits from your tow vehicle. You may have installed too many lights on the trailer...
    view full answer...
  • Trailer Lights Work when Vehicle Is Off, But Do Not Work When Vehicle is On
    That is interesting. What about testing the 4-Way without the hazards on. Instead, have a friend sit in the vehicle and operate each light function with the vehicle off and with the vehicle on. It could be an issue with just the hazards on. I have included a link to a help article that explains how you can go about troubleshooting the trailer wiring. If it is a bad ground, Ground problems normally show up when there is more draw on a system such as when you have the running lights on...
    view full answer...
  • Brakes Not Working on Brand New Identical Travel Trailers with 2 Different Tow Vehicles
    Since the common denominator here is the type of trailer I would say that it is likely there is some issue with that particular model that is causing the problem. It is possible that the brakes need to be broken in. Dexter and Lippert brakes for example require a 200 mile break-in period to seat into the armature and shoe surfaces and must be readjusted afterward. There isn't a fuse or anything on trailers for the brakes. The power gets sent from the vehicle brake controller through the...
    view full answer...
  • Troubleshooting Trailer Taillights that Don't Work Right When Vehicle Headlights are On
    The problem you are having is indicative of a bad ground connection. Ground issues usually show up when there is more load on the system. In this case the constant draw of the head lights is causing too much power draw for the weak ground when you try to use another function. Make sure that the main trailer connector ground and the grounds for all of the lights are attached to clean and corrosion free bare metal surface. Anything placed between a ground wire and the metal frame can interrupt...
    view full answer...
  • Trailer Brake Lights Not Working, All Other Lights Work
    it sounds like you have a blown stop light or trailer brake light fuse. The tow package wiring on a vehicle is separate from the tail light wiring so it makes sense that the truck brake lights are working. Since you have isolated the issue as being on the truck side a blown fuse is the likely culprit.
    view full answer...
  • 7-Way to 4 and 5-Way Adapter # 37385 for the 2005 Toyota Sequoia
    Yes, the Adapter 7 Pole to 4 Pole and 5 Pole, item # 37385, will work with the 7-Way connector on your 2005 Toyota Sequoia. If you have a trailer with surge breaks that uses the 5-way connector you will need to make sure the center pole on your vehicle is wired to the backup light circuit. If it is not wired this way, you will need to splice into the backup circuit behind the taillight and wire to the center pole inside your vehicle connector.
    view full answer...
  • Troubleshooting Boat Trailer LIghts that Don't Function Properly when Headlights are On
    Most likely the problem is an insufficient ground on the trailer's wiring. Anytime you get bizarre trailer lighting functions like what you described when the headlights are on the problem is almost exclusively that the trailer light grounds can't handle the additional load put on the wiring when the headlights are on. Make sure that the trailer side connector are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare...
    view full answer...
  • Troubleshooting Trailer Blinkers That Stay On or Don't Come On at all
    First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester part # 3808 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached. If the voltage checks out there but the trailer lights still don't function right then the problem is on the trailer wiring. That would mean that problem is either due to a ground issue or a short issue. Make sure that the trailer side connector are clean and...
    view full answer...
  • Troubleshooting Trailer Wiring Where Brake Lights Come On with Head Lights
    It sounds like the running light and brake light circuit of your setup is shorting out together somewhere on your setup. Either on the tractor side of the connector or on the trailer. You can test the trailer connector with your circuit tester to see if both the pins are operating independently of each other like they should. If they both are coming on when the headlights are on then the problem is on the truck side of the wiring and you would need to look for a short somewhere before...
    view full answer...
  • Trailer Brakes Come On when Tow Vehicle Automatic Headlights Turn On
    If you are using adapters to match the vehicle side connectors with the trailer side connector it could be that the adapter or the trailer side connector is not wired up correctly to match what is required. I have included a link to a help article that shows how vehicle and trailer side connectors should be pinned out so you can check yours. If the vehicles have brake controllers it could be that the brake controller red wire is not attached to the correct brake switch wire. For hardwire...
    view full answer...
  • Plugging in a Tow Dolly and Magnetic Light Kit to the Same 7-Way Trailer Connector
    You technically could use # 37385 because a 4-Way flat connector will plug into a 5-Way flat receptacle. The last pin just isn't used on the 5-Way end. The only problem is that you have to make sure that the combined power draw is not too much for the tow package wiring on the tow vehicle. The other thing you can do is cut off the 4-Way on the magnetic kit and just splice it into the wiring for the tow dolly. But you would still need to be careful of the power draw. I do not anticipate...
    view full answer...
  • Troubleshooting Trailer Wiring that Works with One Truck But Not Another
    It could be a somewhat weak ground on the trailer that allows the lights to work with one vehicle but not with another. What you can try doing is running a ground wire from each of the light assemblies back to the main ground of the trailer. That should help especially if you have a fold away style coupler on your boat trailer.
    view full answer...
  • Troubleshooting Trailer Taillights that Stop Working When Brakes are Applied
    Sounds like you either have a weak ground on your trailer taillights or the lights themselves are drawing too much amperage and it's causing the circuit to just shut off. Typically a fuse would get blown if this were the case so most likely it's a weak ground. Also, be sure to check the function with the engine of the tow vehicle running as the additional amperage of the alternator running will give the trailer circuits a bit more juice.
    view full answer...

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