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  1. Custom Fit Vehicle Wiring
  2. Hopkins
  3. Custom Fit
  4. Trailer Hitch Wiring
  5. 4 Flat
  6. No Converter
Plug-N-Tow (R) Vehicle Wiring Harness

Plug-N-Tow (R) Vehicle Wiring Harness

Item # 40185
Our Price: $30.81
You Save: 32%
Custom Fit Vehicle Wiring

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40185 - No Converter Hopkins Trailer Hitch Wiring
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  • Reviews (15)
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Hopkins Custom Fit Vehicle Wiring - 40185

  • Custom Fit
  • Trailer Hitch Wiring
  • 4 Flat
  • No Converter
  • Hopkins

Plug-N-Tow (R) Wiring Connectors provide a no-hassle, quick and easy way to wire your vehicle.

  • Replaces the 4-pole trailer connector that is/was already on the truck.
  • Each vehicle-specific connector is pre-wired and uses original OEM connectors for watertight protection, a guaranteed fit, and a great look
  • No cutting or taping
  • 16-Gauge wire
  • 4-Pole connector includes dust cap
  • Easy-to-follow instructions with pictures are included

Can be used with 5-pole, 6-pole or 7-pole adapters.
Tech Tip: It is always a good idea to apply a small amount of grease to all electrical connections to help prevent corrosion.

11140185 Plug-N-Tow (R) Vehicle Wiring Harness

Replaces 40185

This Product Fits The Following Vehicles

  • 2005 - 2008 Ford F-150 without factory trailer connector

California residents: click here

Video of Plug-N-Tow (R) Vehicle Wiring Harness

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

Video Transcript for Hopkins Custom Fit Vehicle Wiring - Trailer Hitch Wiring - 40185 Review

Today we're going to be taking a look at the Hopkins Plug-N-Tow Vehicle Wiring Harness. This product is going to fit a 2005-2008 Ford F150. It's designed to replace the 4-pole trailer connector that was or is on your truck. Each vehicle's specific connector is going to be pre-wired. It's going to use the original OEM connectors for a watertight protection, a guaranteed fit, and a factory look. When installing this, you don't have to worry about cutting or splicing or taping any of your wires. The unit is going to be constructed of 16-gauge wiring.

It's got tape going all around the the wiring, so it's going to stay grouped together. The plugs on the harness right here are going to match up perfectly with the ports on the vehicle. You do get the 4-pole connector on this end. It's got an easy-grip design. It's going to come with the dust cap to protect the connections points when the plug is not being used. On the packaging, it's going to have detailed, easy to follow instructions.

This can be used with 5-pole, 6-pole, or 7-pole adapters. Again, really simple installation. Unplug and remove the currently or previously installed 4-way flap. Then plug in these ports to the connection points. Then you got your new 4-way connector. It's going to come with a couple of zip ties.

That way you can secure any excess or slack in the wiring. It's going to come with your terminal grease. That gets applied to the electrical connections on the vehicle side and the 4-pole connector side to help prevent corrosion to the connection points. That's going to do it for today's look at the Hopkins Plug-N-Tow Vehicle Wiring Harness.

Customer Satisfaction Score:

Customer Reviews

Plug-N-Tow (R) Vehicle Wiring Harness - 40185

Average Customer Rating:  4.9 out of 5 stars   (15 Customer Reviews)

2007 Ford F-150

Great product outstanding service.


Excellent quality


Good quality wiring harness. Held up good , I fish in alot of saltwater so trailer wiring takes a beating. Still in use.

2006 Ford F-150

Went in with no hassle and made my tailgate light work without a hassle. Awesome product.

Light is still lighting up and the product is holding like a champ.
Ray R - 10/10/2018

2005 Ford F-150

Fast service appreciate your getting at here is fast as you did looks great when it warms up a bit I will try putting it in sincerely Mike


2005 Ford F-150

Easy to install and the price was great.

2008 Ford F-150

Very easy install and works great.

2006 Ford F-150

So easy to order and install




Easy to shop, fast shipping, good quality.

2006 Ford F-150


2006 Ford F-150


See what our Experts say about this Hopkins Custom Fit Vehicle Wiring

  • Troubleshooting Tail Lights Not Working When Brakes are Applied on a Boat Trailer
    It sounds like you have a ground issue on your trailer with new lights. It sounds like when the lights are drawing their maximum amperage (when the brake lights are on) the draw is too much and it is shorting out the lights. I would check the wiring for the lights, especially the ground wires, for loose wiring or not being grounded to a clean surface and fix as necessary. If the grounds are good, the other potential problem is that you might be using too many lights on your boat trailer,...
    view full answer...
  • Trailer Lights Not Fully Working on a Trailer Towed by a 2007 Ford F-150 with Factory Tow Package
    It does sound like a ground problem. Most wiring issues are due to a bad ground connection. But first, I do recommend checking the trailer and vehicle side connectors for dirt or corrosion in and behind the plugs. That can cause the problem as well and it is the easiest thing to check. After that, if you still have issues, start checking all of the grounds starting with the truck side trailer connector and working back to the tail lights on the trailer. The grounds should all be connected...
    view full answer...
  • Trailer Left Turn and Tail Light Not Working on a Trailer Towed by a 2006 Ford F-150
    What I think may be happening is there is the absence of a relay that will not allow certain functions to work on the trailer lights if the load on the system is great enough. I would consult the owners manual, find the location of any relays/fuses associated with the trailer wiring, and make sure they are in good working order or add the ones that may be missing. Another issue could be a faulty ground somewhere since your ground test did get it to partially work. You will want to check...
    view full answer...
  • No Left Hand Turn Signal On a 2006 Ford F-150
    If you don't have power on the left hand stop/turn signal pin on the trailer connector for your 2006 Ford F-150 then you likely either have a blown fuse or a loose/severed wire. The fuse for this circuit is located in the engine bay fuse box, slot 42 which is a 10 amp fuse. If this fuse is good then check the wires at the back of the trailer connector and work your way back to see if any breaks are present. If you still can't find anything wrong then you may just need to replace the...
    view full answer...
  • Troubleshooting Truck Blinkers that Only Blink Once when Trailer is Connected
    If I am understanding you correctly it sounds like when your trailer is connected to your truck and you activate either blinker your truck's blinker only blinks once then stops. This would lead me to believe that your blinker circuit is getting overdrawn by the trailer circuits which is preventing them from working. What I would recommend you do is replace your current trailer blinkers with LED blinkers as they will draw considerably less power than incandescent bulbs which should prevent...
    view full answer...
  • Troubleshooting 2013 Ford F-150 Trailer Wiring that Blinkers Stopped Working
    Sounds like you may have some blown fuses under the hood of your 2013 Ford F-150. Check the fuse box for trailer wiring fuse locations and replace as necessary as it sounds like the turn signal circuit fuses have blown. This circuit most likely blew from a short circuit on your trailer wiring. Before you reconnect your trailer wiring I would check the wiring for the turn signals and fix any cut or exposed wire on the circuit that could be causing the short.
    view full answer...
  • Replacement 4-Way Recommendation for a 2006 Ford F-150
    The Hopkins 4-way part # 40185 has been confirmed as a fit for your 2006 Ford F-150 and would work well for you. It has a ground wire built into the harness connectors so it would not require the use of an additional ground wire.
    view full answer...
  • Troubleshooting 2005 Ford F-150 Taillights Not Functioning After Trailer Wiring Install
    The Plug-N-Tow # 40185 that you referenced has been confirmed as a fit for your 2005 Ford F-150 so if installed properly it should work just fine. Normally when what you described happens the problem is that the wiring harness just isn't making a good connection and would just need to be double checked that it is plugged in properly. Since you were having issues with your trailer wiring prior the problem could be something else related to the lighting of the truck. However, typically...
    view full answer...
  • Brake and Turn Signal Lights do Not Work on Boat Trailer
    Since the trailer lights are working with a different vehicle, that would indicate an issue on the truck side. But it could also indicate a problem with the adapter as well. You will want to check to make sure the adapter is pinned out correctly to match the way the trailer and truck are configured. Make sure the trailer connector on the truck is clean and free of corrosion. On a 7-Way corrosion can also build up behind the connectors where the wires attach. Check the owners manual for...
    view full answer...
  • Left Turn Signal Not Working on 2012 Ford F-150 4-Way Trailer Connector All Other Functions Work
    You may have a bad relay in your 2012 Ford F-150. Under the hood in the power distribution box check the relay in location 37. The easiest way to see if a relay is bad is to use a known good one in its place. You may have to get this relay from a Ford dealer.
    view full answer...
  • Trailer Running Lights Do Not Work When Connected to a Honda CR-V
    So it sounds like you are using an adapter like # 37185 or something similar. You need to make sure the adapter is grounded to the vehicle frame otherwise it will not work properly. It could also be a ground issue on the trailer. 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 a turn signal or brake light. Make sure that the vehicle side and trailer side connectors are clean and free of...
    view full answer...
  • Will The Tow Package Vehicle Wiring Harness with 7-Way Trailer Connector Fit My 2005 Ford F-150
    The Tow Package Vehicle Wiring Harness with 7-Way Trailer Connector for the 2004 F-150, item # 118247, will not work on the 2005 model year Ford F-150. There was a were changes for the 2005 model year and the wiring package was changed on the Ford Trucks. To wire your vehicle for a 7-way connector you will need a 4-way connector first. If your truck has a factory 4- way connector then you will be able to use our Adapter 4 Pole to 7 Pole and 4 Pole, item # 37185, and splice into the vehicle...
    view full answer...
  • Availability of 4-Flat Trailer Wiring for a 2006 Ford F-150
    If your 2006 Ford F-150 has a factory tow package, the Hopkins Custom Fit Vehicle Wiring, # 40185, that you referenced is the correct harness. If your truck does not have a factory tow package, you will need Draw-Tite Wiring, # 18252. This is a hardwire 4-Flat. You will need access to the taillight wiring. The yellow wire is left turn and stop. The brown wire is running lights. The green wire is right turn and stop. The white wire is ground. If you just need to replace a broken 4-Way,...
    view full answer...
  • Trailer Turn Signals and Brake Lights Not Working on a Boat Trailer
    If you are getting the correct signals from the truck side trailer connectors, then the problem is on the trailer. There could be a number of issues causing the problem. The easiest to check would be the trailer side connector. With the trailer connected, test the wires right behind the trailer side connector using a circuit tester like # PTW2993. If no signals are coming through, then you know the connector is bad and it will need to be replaced. While you are at the trailer side connector,...
    view full answer...
  • Lights Not Working on Camper Towed by 2004 Ford F150 Using 4-Pole To 7-way Adapter
    You said that the adapter is getting power, but is the 7-way on the adapter putting out power on the lighting circuits? You'd need to use a circuit tester like part # PTW2993 on the 7-way as each taillight function is activated, to check it. If the 7-way on the truck tests out okay, but won't work on the trailer (which works on other vehicles) try using the truck with a different trailer if possible. This will 100 percent rule out the truck as being the problem. You still might have a...
    view full answer...
  • Trailer Turn Signals and Brake Lights Stopped Working with 2005 Ford F-150
    The first thing to check is the trailer connector on your 2005 Ford F-150. With the trailer disconnected use a circuit tester such as # PTW2993 to test the vehicle side connector while someone sits in the cab of the truck and activates the turn signals and brake lights. If there is power at the truck side connector, then the problem is on the trailer. Make sure that the truck and trailer side connectors are clean and free of corrosion inside where the wires attach and outside on the pins....
    view full answer...
  • Trailer Running Lights Do Not Work When Connected to a 2011 Ford F-150
    First, check to see if the running light circuit on the 7-Way on your 2011 Ford F-150 has power using a circuit tester such as # PTW2992. If it does not then there is likely a fuse blown or blown or missing relay. Use the owners manual to locate any fuses/relays related to the tow package wiring. If there is power on the truck side connector then plug in the adapter and make sure there is power on the outside of it. If there is not then the issue is with the adapter. If there is power...
    view full answer...
  • Right Turn Signal and Brake Light Not Working on a 2003 Boat Trailer
    This sounds like a classic bad ground problem. To make sure it is a problem on the trailer and not the vehicle, disconnect the trailer and test the trailer connector on the vehicle. Use a circuit tester like # PTW2993 if needed. Have someone sit in the vehicle and run through the functions. If everything is working on the vehicle connector then that would indicate an issue on the trailer, probably a bad ground. If the trailer connector on the vehicle is not showing the correct signals...
    view full answer...
  • Troubleshooting Left Turn/Brake Lamp on Trailer Towed by 2007 Ford F150
    As a first step, you will want to determine if the problem is on the vehicle or in the trailer wiring. Use a circuit tester like part # PTW2993 and test the pin on the trailer connector fed by the yellow wire while the turn signals are activated. This pin should light up with the turn signal and when the brake pedal is pressed. If this pin does light the tester, the problem exists with the trailer wiring. You will need to trace yellow wire that feeds the driver's side turn signal and...
    view full answer...
  • Brake Lights and Turn Signals Do Not Work on a Trailer Towed by a 2012 Dodge Durango SXT
    The easiest way to see if the issue is on your trailer or on your 2012 Dodge Durango SXT is to use a circuit tester like # PTW2993 and test the pins on the 4-way connector on your vehicle with the trailer disconnected. Assuming the vehicle was wired properly, you should be able to use the 4-way connector or the 7-way connector. Have someone active the turn signals and brakes as you test each pin on the 4-way connector on your vehicle. I have attached a video of my co-worker demonstrating...
    view full answer...
  • Blown Fuse & Relay with New Utility Trailer Running Lights
    One possibility is that the running lights on the new trailer are simply drawing too much current and are blowing the fuses. Trailers can be equipped with either high-efficiency LED lights or standard incandescent bulbs, which draw about 10 times the power. If the new trailer has many more running lights than the boat trailer, and/or if they are incandescent types, then they may be overloading the vehicle wiring. It is also possible that the running light wiring is pinched, has a bare...
    view full answer...
  • Trailer Brake and Turn Signals Not Working When 7-Way Connector Plugged into 2011 Ford F-150
    I would recommend checking the fuse box in your friends F-150 to make sure it has the fuses/relays installed for the trailer stop and turn lights. I looked up a fuse box diagram for a 2011 F-150 and it looked like the trailer tow left stop/turn relay is at location 37 and the trailer tow right stop/turn relay is at location 38. You will want to check the legend in the fuse box of your friend's vehicle to make sure those are the correct locations. I would also recommend using a circuit...
    view full answer...
  • Troubleshooting Malfunctioning Turn Signals on Utility Trailer Towed by 2006 Chevy Silverado
    The first thing you will need to do is to test the 4-pole connector on the truck with a circuit tester like # PTW2993. This will tell you if the wiring problem exists on the truck or on the vehicle itself. The pins on the connector fed by the yellow and green wires should light up your tester when the right turn, left turn and brake lights are activated. If you do not get any signal on the right or left turn pins, you most likely have a blown fuse. Check the fuse box under the hood. If...
    view full answer...
  • Troubleshooting Trailer Stop and Turn Lights
    On a 4-pole trailer connector like # 40185 brake and turn lights are carried on the same wire; yellow for the left brake and left turn light and green for the right brake and right turn light. Running lights for both sides of the trailer are carried on the brown wire. Since you tested your truck connector with a circuit tester like # PTW2993 and found that the correct signals are present on the pins for the yellow and green wires when you activate the brake and turn light functions, this...
    view full answer...

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