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Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter

Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter

Item # PK12742
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Lowest Prices for the best trailer wiring from Pollak. Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter part number PK12742 can be ordered online at or call 1-800-940-8924 for expert service.
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Pollak Trailer Wiring - PK12742

  • Wiring Adapters
  • Single-Function Adapter
  • 4 Flat
  • Plug Only
  • 7 Round - Round
  • Pollak


  • 7-Pole round pin to 4-pole flat connector adapter
    • Promotes quick and easy conversion of 7-pole connector to 4-pole flat connector
    • Allows 1 vehicle to tow either campers or boat trailers without electrical brakes
    • Connects Ground, Left Turn, Right Turn and Stop circuits
  • Non-corrosive nylon shell and insert


  • Application: Vehicles with 7-pole, round pin connectors
  • 1-Year limited warranty

12-742EV Pollak 7-Way Round Pin to 4-Way Flat Connector Adapter

12-742EV Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter

Video of Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter

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

Video Transcript for Pollak Wiring - Wiring Adapters - PK12742 Review

Today we're going to be taking a look at Part# PK12742. This is the Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter. It's going to promote quick and easy conversion of your 7-pole connector to the 4-pole flat connector. It's going to allow one vehicle to tow either campers or boat trailers without electrical brakes. Now it does connect the ground left turn, right turn and stop circuit, so you can see here that the 7-pole round pin portion only has the necessary contacts installed to power or send signals to the 4-pole flat connector. It's going to be made from a non-corrosive nylon shell as well as the insert, that's made from the same type of material. It's going to feature the easy-grip design, so that's going to make connecting and disconnecting really simple and easy on you.

If we take a measurement of the overall length measuring from edge to edge, that's going to give us a measurement of about 4 1/4 inches and this is designed for vehicles with 7-pole round pin connectors. You can see again that the 7-pole round pin portion only has the necessary contacts installed for the 4-pole flat connector. Very simple connection. All you have to do is plug the 7-pole portion into place with the connector and then here on the back side, you're going to have the area when you'd make the 4-way flat connection just here at the rear of the plug. That's going to do it for today's review of Part# PK12742. This is the Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter.


Customer Reviews

Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter - PK12742

Average Customer Rating:  5.0 out of 5 stars   (24 Customer Reviews)


Great service in a reasonable length of time. Good to say in today’s world. etrailer is top five on internet for sales and service.


Well made product; customer support is responsive; quick shipping.


Have not tried it yet but it looks to be well made.


Great products fast shipping great customer service


I ordered the 7 way wiring harness and needed this item to qualify for free shipping . The web site is great, and the guy I called in customer service was great. Much less price than from the dealer.


I haven't had a chance to try the product out as of yet, but, with that said, the service I received from etrailer was unbelievable! I have never had better internet service in my life. Thanks for being so professional. Take care,


We received the product on time and it performed as designed.
If all my vendors were as efficient as I would never have anything to worry about.
I would recommend etrailer to anyone.


I was unsure ordering this adapter - ETrailer was the only place I found that carried it. I was very pleased when it fit and worked perfectly. It is solid and easy to grip to install or remove it.


This is a high quality product and fits perfectly. Works great with my trailer. Fast shipping and great packaging. I will absolutely purchase from etrailer again.


Great adapter from my truck to my boat trailers.


Perfect fit. just make sure before buying you are ordering the correct plug. there are many to choose from. Mine choice was correct. It works great and will be used for many years to come. Thank you.




the right product with 7 round holes. hard to find


A great product, works great. Shipping was fast. Would buy again.


Great selection, quick delivery what else could you want.





It's the one I ordered and it works


Will work perfectly


Quality products from an outstanding company. Orders are filled and shipped quickly with no hassle.





Ask the Experts about this Pollak Trailer Wiring

  • Troubleshooting Vehicle Trailer Wiring Where Stop and Turn Signal Circuits aren't Functioning
    Yes, first thing you would want to do is check the towing wiring related fuses under the hood of your vehicle. Most likely you blew a fuse or relay and that is where the problem is. You can also check for corrosion on the trailer connector and clean off as necessary.
    view full answer...
  • Will Pollak Adapter Connect With 7 Pin Round?
    By "John Deere 7 pin connection" I assume you are referring to the 7-way round that is common among agricultural trailers. If so, the Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter # PK12742 will fit into that connection. I've added a link to a video review of this product for you to take a look at.
    view full answer...
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  • Troubleshooting Brake Lights not Lighting On Trailer When Using a 7 to 4-Way Adapter
    On a 7-Way and 4-Way, the brake light function is on the same wire as the turn signals. So if your turn signals are working, then the connection is made, there is just a problem that is not allowing the brake lights to function. Most likely, there is a bad ground. First check that the ground on the vehicle side 7-Way is attached to a bare metal surface and is free of dirt and corrosion. Next, check the trailer side 4-Way ground and make sure it, too is attached properly and free of dirt...
    view full answer...
  • Does 4-Way to 7-Way PK12742 Fit 7-Way Round with Upper Pin that is Larger
    The upper pin of the 7-way round that you have is the ground pin which normally is larger and is perfectly compatible with the # PK12742.
    view full answer...
  • Adapter Availability 13 Pin European to 4-Way US Trailer Connector
    Unfortunately we do not have an adapter to go from a European 13-way trailer connector to a U.S. style 4-way trailer connector. European trailers typically have separate brake light and turn signal circuits, but U.S. trailers use a combined wiring system that use one wire for the turn signals and brake lights. You could make an adapter using a universal 4-way flat tail light converter like part # 119130, but you would need to find a European trailer side 13-way connector that can be...
    view full answer...
  • No Left Turn or Left Brake on Rewired Trailer When Connected To 7-Way on 2013 Porsche Cayenne
    You can test the 7-Way connectors on the Porsche Cayenne or Mercedes ML250 and the trailer with a circuit tester, part # 40376. I am including a link to a FAQ page on trailer wiring that will show you the functions of each pin on your connector, depending on if it is either a 4-Way, 5-Way, 6-Way, or 7-Way. This will help you determine if there is a problem with the wiring on the vehicle or the trailer. If you are using the Pollak 7 Round to 4 Flat Wiring Adapter, part # PK12742, you will...
    view full answer...
  • Does 7-Pole to 4-Way Trailer Adapter Have Converter Built In?
    The Adapter 7-Pole Round Pins To 4-Pole Flat # 47405 will not have the converter built in to combine your separated turn signals and stop light. That adapter will require a separate converter. For an option with the built in converter use the Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter # PK12742.
    view full answer...
  • 13 Pin EU Trailer Wiring Harness to 4 pin US Trailer Wiring Connector.
    There is not a simple adapter to plug into your existing 13-pin connector to convert to a US 4-pole connection. You can use a Tekonsha # 119130 harness which has a 4-pole connection on one end and wires to splice into your tow vehicles lighting system. I have attached a video that discusses the installation
    view full answer...
  • Brake Lights Not Working on 2014 Chevrolet Equinox Being Towed by Semi Road Tractor
    Since your 2014 Chevrolet Equinox has a combined wiring system, which means brake and turn signals are sent along the same wire, you will need to use the Upgraded Circuit Protected Taillight Converter, # 119178, in order for your brake lights to function. You will want to use a connector like the Pollak HD 7-Pole Round Pin Connector w/Cable Guard, # PK11702, and wire in taillight converter, # 119178, to match the functions of the 7-way on your semi. I have included a diagram that shows...
    view full answer...
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  • Adapting a 7-Way Round Pin Connector on a 1992 Ford F-150 to 7-Way Blade Style Connector
    To adapt a 7-Way round pin vehicle side connector to a 7-Way blade style connector use adapter # PK12-724. The adapter will route the functions to the proper pins on the output side so you would not have to move any wires around.
    view full answer...
  • 7-Way Round to 7-Way Blade Adapter Recommendation for a 1993 Ford F150 Towing Travel Trailer
    What you have on your 1993 Ford F150 is a round 7-way, and it sounds like your travel trailer has a blade style 7-way. All you need is the correct adapter and you would be good to go. For that you would want the Pollak Trailer Connector Adapter # PK12-724. You will need to cut the red and blue wire and reattach them opposite. So the red wire to the blue wire and the blue wire to the red wire so that the wiring matches what you currently have.
    view full answer...
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  • Trailer Wiring Adapter Recommendation for going from a 7-Way Round to a 4-Way Flat
    Sounds like your Eager Beaver trailer has a 4-way trailer connector and your dump truck has a 7-way round. All you need is the correct adapter. For that you would want the Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter # PK12742.
    view full answer...
  • Which Pollak 7 Pole to 4 Pole Flat Wiring Adapter will Fit My 1993 Ford F-150 with Factory 7-Way
    The adapter you are looking at is for round-pin 7-Way connectors. Blade or flat pin 7-Ways are far more common on pick-ups. To my knowledge, Ford has not offered a 7-Way round Pin on an F-150, but I have no way of checking that Ford part number you provided. If you determine that it is a 7-Way blade pin, the adapter you need is part # PK12716.
    view full answer...
  • Troubleshooting the Wiring and Pollak Adapter on New Jet Ski Trailer
    I would start off by checking the ground for the jet ski trailer as well as the ground for the right tail light. Make sure that these have a good, solid connection to a clean metal surface on your trailer. If the right tail light still isn't functioning, I recommend using a circuit tester like # 40376 to check the functioning of the Pollak 7 Pole to 4 Pole Adapter, # PK12742. If everything is functioning as it should on the adapter, I would check the trailer connector to make sure that...
    view full answer...
  • 7-Way to 4-Pole Trailer Connector Adapter for 2013 Porsche Cayenne
    If your Cayenne has the 7-way connector, you will simply need an adapter to convert it to a 4-pole. Because your Cayenne is equipped with a bulb-out sensor, if your trailer has LED lamps you will need to use an adapter with a resistor in it like part # TR20141. LED lamps draw very little power, and fool the bulb-out sensor into thinking a bulb is burned out. This will make the turn signals hyper-flash. If your trailer uses incandescent lamps, you can use any of the other 7-way to 4-pole...
    view full answer...
    Image 1 for
  • 4-Way Trailer Wiring Connector Recommendation for 2015 Porsche Cayenne
    To install a 4-way on your 2015 Porsche Cayenne I recommend the ZCI kit part # 119250KIT as it installs without any splicing. 4-ways don't have doors so in case you have a 7-way and need an adapter to give you a 4-way you'd want the # PK12716.
    view full answer...
  • Troubleshooting Wiring for a 1998 Ranger Trailer 7-Pin Round to 4-Flat on a 2011 Chevy Tahoe
    There are a couple of potential issues as to why your turn/brake lights aren't working. First you will need to determine where the problem is coming from and to do that test the vehicle side of your trailer connector. Use a 12V circuit tester like # 40376 to check the function at your 4-way plug such as # HM48110. Having a friend sit in your 2011 Chevy Tahoe to engage each function while you test. If functions are good, test the 1998 Ranger trailer because your 4-way will be okay. If...
    view full answer...
  • Parts Needed To Install A Cargo Carrier Light Kit That Plugs Into A 7 Way Round Connector
    What you're going to need is a light kit like # 20174, and a 4 pole to 7 way round adapter # PK12742. Simply plug the 4 pole trailer connector from the lights into the adapter, and then plug the adapter into your 7 way round connector on your 2006 Chevrolet Express. The harness on the light kit # 20174 is 6' long, and the off-set Y-harness is 3' long, which should be plenty long for you.
    view full answer...
  • Recommended European 7-Way Round to 4-Way Flat Wiring Adapter for 2006 Porsche Cayenne
    It sounds like you will instead need the Tow Ready # 118710. This plug adapter will fit into the 7-way round European-style trailer connector with recessed sockets and adapt it to the 4-way flat you desire. The only catch is that this harness will only work for combined wiring so you will want to check your factory harness by testing the pins with a circuit tester like # 40376 to see if both the brake and turn signal are carried on the same pin. If they are then this adapter will work...
    view full answer...
  • Wiring Adapter for a 1997 Land Rover Discovery with 7-Way Round Pins
    Trailer Connector Adapter # 118710 is an odd duck but not as odd as what you have on your 1997 Land Rover Discovery! Actually, it isn't that odd. It is a 7-Way round pin but I wasn't expecting it to be on that particular vehicle. The design of it though is unique. First, make sure it is active by testing those pins using a circuit tester such as # 40376 or a meter if you have one. If you have power with the various vehicle lights on then you will need adapter # PK12742 to go from a 7-Pole...
    view full answer...
    Image 1 for
  • Troubleshooting Stop/Turn Signals Not Functioning on a 2005 Porsche Cayenne with LED Trailer Lights
    First thing you want to do is test the 7-way on your 2005 Porsche Cayenne with a circuit tester like our part # PTW2993 to determine if the lighting functions are working correctly on the connector. See the attached picture to see what pin carries which circuit. You will want to have a buddy apply the different taillight functions of your Cayenne and then using the circuit tester check the appropriate pin for voltage. If this check out then you know the vehicle wiring is not the problem. Have...
    view full answer...
    Image 1 for
  • Creating Adapter to Go From 7-Way Round to 4-Way Flat
    The 7-way round connector is odd as it typically means the vehicle has the stop lights and turn signals on separate circuits which is the opposite of what trailer wiring has so you'd need to come up with an adapter since there isn't one ready-made. If this is the case you can build an adapter using the part # RM-732 as a signal converter. You will need a round pin male connector, # PK11702 and then the part # W787264 for a 4-way. Basically you will be splicing the converter between these...
    view full answer...
  • Does a 4-Way Wishbone Trailer Wiring Harness Require a Special 7-Way to 4-Way Adapter
    If the RV has a 7-Way, blade style connector, you can use any 7 pole to 4 pole adapter like # PK12716. If the RV has a 7-Way round pin trailer connector, you can use Pollak 7 Pole Round Pin to 4 Pole Flat Wiring Adapter, # PK12742. The 4-Way wishbone trailer wiring harness, # A35W42B, does not require a special adapter, even though it has 5 wires. In a wishbone harness, the running light circuit is split at the connector with one wire (yellow/brown) going to the left side and the other...
    view full answer...
  • Adding a 7-Way to 2013 Porsche Cayenne
    To add a 7-way to your 2013 Porsche Cayenne that will allow you to pull a larger trailer and use a brake controller I recommend the 7-Way RV Upgrade Kit # ETBC7L. This is very similar to the Universal Installation Kit # ETBC7 with the difference being that you will not have to wire the lead from the brake controller to the brake output pin on the 7-way. This will make installation easier but keep in mind there are only certain brake controllers that the 7-Way RV Upgrade Kit # ETBC7L will...
    view full answer...

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