bing tracking image
  1. Trailer Wiring
  2. Optronics
  3. Trailer Connectors
  4. Trailer End Connector
  5. 4 Flat
  6. Plug and Lead
35 Ft 4-Way Trailer Wiring Harness - Wishbone Style - 42" Ground

35 Ft 4-Way Trailer Wiring Harness - Wishbone Style - 42" Ground

Item # A35W42B
Retail:$25.47
Our Price: $20.92
You Save: 18%
Trailer Wiring
Shipping Weight: 1.19 lbs
Add to cart
In Stock
zoom in icon
slider vertical icon
zoom out icon
Comment field cannot be left empty.
Name field cannot be left empty.

Thank you! Your comment has been submitted successfully. You should be able to view your question/comment here within a few days.

Error submitting comment. Please try again momentarily.

Product Images

In Use/Installed

Customer Photos

Need help with installation?
Locate installers near me
4-Way trailer harness connects to your tow vehicle to control trailer light functions. Wishbone-style harness comes with 2 tail light wires split for simple wiring. Great Prices for the best trailer wiring from Optronics. 35 Ft 4-Way Trailer Wiring Harness - Wishbone Style - 42" Ground part number A35W42B can be ordered online at etrailer.com or call 1-800-940-8924 for expert service.
  • All Info
  • Reviews (754)
  • Q & A (0)
  • Photos

Optronics Trailer Wiring - A35W42B

  • Trailer Connectors
  • Trailer End Connector
  • 4 Flat
  • Plug and Lead
  • 31 Feet and Longer
  • Optronics

4-Way trailer harness connects to your tow vehicle to control trailer light functions. Wishbone-style harness comes with 2 tail light wires split for simple wiring.


Features:

  • 4-Way trailer harness connects to your tow vehicle to control trailer light functions
  • Wishbone-style harness comes with 2 tail light wires split for simple wiring
    • Allows you to run wires separately down each side of the trailer to tail lights without needing a jumper wire
  • Color coded wires help with installation
    • White - ground
    • Brown - tail lights
    • Yellow - driver side stop/turn
    • Green - passenger side stop/turn


Specs:

  • Wire harness length: 35'
  • Ground wire length: 42"
  • 3-Year Warranty


Manufacturer Cross Reference
Harness will work as an exact replacement for:

  • Truck Lite # 108835
Wishbone Wiring Diagram


A35W42B Optronics 35 ft. Wishbone 4-Way Trailer Wiring Harness with 42" Ground Wire

Alternate part number: A-35W42B




California residents: click here


Customer Satisfaction Score:


Customer Reviews

35 Ft 4-Way Trailer Wiring Harness - Wishbone Style - 42" Ground - A35W42B

Average Customer Rating:  4.8 out of 5 stars   (754 Customer Reviews)

4-Way trailer harness connects to your tow vehicle to control trailer light functions. Wishbone-style harness comes with 2 tail light wires split for simple wiring.

by:

Works very well after re-wiring trailer lights with waterproof distribution box.



by:

2 things. 1st@: I think there should be an option to pick tinned wire. 2nd: The ring terminal for the ground needs to be bigger.



by:

Made it easy to rewire old 16 foot trailers with extra wire to reroute it better.



by:

Worked out great. Direct replacement for my old 4-way boat trailer harness that had corrosion damage at a quick splice joint causing my trailer marker lights to not work. Easy to follow wiring diagram from etrailer store page.



by:

Item as describe. Work Fantastic!!!!!!! !!!!!!!



by:

I want to thank you for all your help with my trailer you were more helpful than you realize. So this is my trailer for a 22' Flats Cat shallow draft Catamaran. I totally dismantled my trailer and buffed by hand with a wire buffer and sand blasted in some spots and applied multiple coats of some very expensive galvanize paint (Z.R.C.). I installed all new C. E. Smith Carpet (about 80'), seven new LED waterproof lights, new springs, new equalizers, new tongue jack, new wench, new safety chain, new chain brackets, all new SS hardware and a 35' long wiring harness.
I was able to send only one review with a picture of the safety chain and brackets. I'm having a little trouble with the rest..oh some of these items were bought locally or from your competitors, until I found ETRAILER. Your prices were cheaper for the exact same things. Your helpful how to videos were helpful. And Rose, your personal helpful knowledge made my buying experience very pleasant, I actually enjoyed talking to you! Thanks to ETRAILER and specifically to Rose G.



by:

items are exactly as shown on website. I made a phone call to clarify if my application suited the part. Friendly knowledgeable Shipping price & delivery excellent



by:

Great product very easy to install my order arrived 3 days early I received emails so I was informed when my wiring harness was shipped and one when it was delivered Thanks E Trailer A happy customer!!!



by:

1 year, and so far so good. I have had cheap harnesses before that would oxidise from the inside out and break when connecting flat 4, but this one is doing fine.



by:

The plug looks and feels solid! This is the only place that had a long enough wiring harness to do what I needed. Shipping was also very fast!

Eric

1/29/2019

After one year, It is still working great! It makes all the difference having long enough wires to where there is no splicing on a saltwater boat trailer.



by:

Perfect! Just what I needed!!
I could
only find a harness plug with one brown wire (4 wires total) at my local stores. I "googled" the problem I had (my harness plug had 2 brown wires). A rep from etrailer had answered someone's same question on a message board. It was a detailed explanation as to why one would need this part. Then the rep put a link to the etrailer site. And there is was, the harness plug with 2 brown wires (5 wires total) and at an agreeable price to boot!!!!! And now I know about the etrailer website!!!!



by:

Replaced the wiring and lights on my 1992 boat trailer. I was able to get everything needed from etrailer. I think Optronics is of the highest quality
and recommend both etrailer and Optronics product.



by:

It all worked as advertised good instru ctions.



by:

The white wire needed to be a bit longer, but I made it work, other than that a



by:

This worked great, had to rewire my trailer after having it painted and reconfigured and this item was long enough and allowed me to tie in my additional lights.



by:

The wiring harness arrived quickly and was installed with ease.



by:

Came on time long enough for 23' boat



by:

Absolutely Fabulous! Exactly what I was looking for but couldn't find at any retail store in my area! The wishbone design splits the brown wire at the plug. Makes wiring both sides of the trailer with no splices or having to find additional brown wire sold by the foot!



by:

I am giving this item an Excellent review based on my former (very positive) experience with your products, but actually I haven't used it yet. My former harness is still working. I will use this as a replacement when the time comes.



by:

Item was exactly as described and just what I needed to rewire my trailer. I also appreciate the great customer service as I was emailed instructions to aid me in the installation of the item ordered.



by:

High quality, fairly priced, totally sa tisfied!



by:

When it was time to rewire our 2007 boat trailer I selected the wiring harness from etrailer because of its wishbone configuration, long ground wire and quality. We used an electrical fishing tape to pull the wire through the channels of the trailer and it was straight forward and relatively easy. It has worked just fine and we have no complaints. Great price and fast service too.



by:

This harness is exactly what you expect to receive when you order it.



by:

This harness has a heavier gawg than the box store brands. Rseems to be good quality.



by:

A basic wiring harness, meets its purpose very well. Arrived on time.


25
754
Show More Reviews

See what our Experts say about this Optronics Trailer Wiring

  • 40' Wishbone Trailer Wiring With A Ground Wire Running Down Both Sides
    We do not offer wishbone wiring that has a ground wire going down both sides. You really don't need it because the ground wire is for the plug itself not the lights and you want the ground close to the plug. I recommend using the 4-Way Wishbone Trailer Wiring Harness Item # A40W42B.
    view full answer...
  • Converting 7-Way Blade To 4-Way Flat On Trailer
    Yes, it is possible to convert your 7-way on your trailer to a 4-way. To replace the wiring on your Coleman 10 Foot pop up camper we offer wiring adapters that allow connection of different formats of trailer wiring. The best option to change the wiring on your trailer to match the 4-Flat on your Xterra is to cut off the 7-Way blade, and then install (them in) a trailer side 4-Way # A35W42B. The right turn function is the GREEN wire, the left turn function is the YELLOW wire, The trailer's...
    view full answer...
    Image 1 for
  • Trailer Lights are Dim When Connected to Truck
    Sounds like you have a ground issue on your 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 but can show up any time. Locate the main trailer ground wire. Disconnect the wire and clean the surface that the wire is connected on your trailer. Make sure that the connection is on bare metal. No rust, paint, dirt, or grease on the trailer's surface where...
    view full answer...
    Image 1 for
  • What Wire Gauge is Used on the 35 ft. Wishbone 4-Way Trailer Wiring Harness, # A35W42B
    I went out to the warehouse and pulled a 35 ft. Wishbone 4-Way Trailer Wiring Harness, # A35W42B, and used a wire gauge tool to measure the wires. The copper wire itself is 20 gauge. If you measure the wire with the insulation on it then it is thicker but wire gauge corresponds to the strands not the insulation part.
    view full answer...
  • Troubleshooting Trailer Wiring Brake Circuit Signal that Stopped Working After 7-Way Replacement
    Since the trailer is no longer able to recognize a trailer connection the issue is most likely that the brake output circuit of the wiring was damaged when the old one was yanked out. This is a fairly common issue so you'll need to go over the wiring looking for any shorts or broken wire and fix as needed.
    view full answer...
  • Wiring Brakes On Tandem Axle Trailer
    Typically trailer wiring is color coded. The brake circuit is usually a blue wire which travels to each brake magnet, where it is attached to one wire from each brake magnet. The other wire from each brake magnet will ground to the trailer frame. I have attached a drawing that shows how the wiring is typically run for brakes on a trailer. I have also attached a link to trailer wiring diagrams that may help.
    view full answer...
    Image 1 for
  • Troubleshooting Trailer Running Light Circuit that Turns Off When Interior Lights are Turned On
    Your problem is due to your trailer wiring ground circuit being insufficient. Basically you are trying to draw more amperage than you ground circuit is capable of keeping up with so it's shutting down partially. Since the interior lights and running lights are on separate circuit it wouldn't be an overdrawing of either circuit so it's definitely a weak ground. So you need to improve the ground of the trailer wiring. You can do this by running jumper wires from the circuits back to the...
    view full answer...
  • How To Convert A Wishbone Trailer Wiring Harness To A Regular 4-Flat Trailer Wiring Harness
    It sounds like you have a wishbone wiring harness install on your trailer. A regular 4-way wiring harness has 4 wires from the back of the connector, 1 for left turn/brake typically (yellow), 1 for the right turn/brake typically (green), 1 for the tail lights typically (brown), and 1 for the ground typically (white). A wishbone 4-way connector has 5 wires, 1 for left turn/brake typically (yellow), 1 for the right turn/brake typically (green), 2 for the tail lights typically (brown w/ yellow...
    view full answer...
  • Availability of 40 inch + Long Wishbone 4-Way Trailer Wiring Connector
    Sounds like you are in need of a wishbone 4-way harness to replace what you have on your trailer. The two wires that run to the one pin are the running lights. We have a 42 inch long version of what you need, part # A35W42B. This is the longest harness we offer.
    view full answer...
  • Troubleshooting Trailer with LED Taillights Where all Lights Shut Off When Running Lights are On
    I'd be willing to bet you have a short on the running light circuit of your trailer wiring that's touching the trailer frame which is causing your problems. Since the lights are grounding through the frame a short to the ground of all of the circuits will take out all of the lights that are using the frame as a ground. Go over the running light circuit looking for any cut or exposed wire and fix as needed.
    view full answer...
  • Troubleshooting Dim Blinking on Left Turn Signal When Right Turn Signal On
    More than likely this is a short in the trailer wiring or corrosion on your connector. Go ahead and inspect your connector on the trailer and vehicle side. If any corrosion is present, it is possible power is moving over causing both to run at the same time. One way or another it would be a good idea to clean both. After you check the connectors, go ahead and make sure your ground wire is secure. This is an easy thing to check and the source of many problems. Assuming your ground is in...
    view full answer...
  • Troubleshooting Trailer Brakes that Lock Up When Connected to Junction Box
    Sounds like you are wiring the brake output circuit from your brake assemblies to a pin on the junction box that carries the 12 volt circuit and not the brake output circuit. You need to make sure that you have the right circuit for the brakes on the junction box.
    view full answer...
  • All Trailer Lights Blink With Turn Signal on 2007 Triton ATV Trailer
    The fact that you have an aluminum trailer could be the problem. Aluminum does not make for a good ground. What I recommend is to located the ground wires at the backs of the lights and attach jumpers from the grounds to the main trailer connector ground. This is a common issue with aluminum frames, tilt trailers, and trailers with folding tongues. Also check the towing vehicle and trailer connectors for dirt and corrosion. Corrosion could cause a short or even a bad ground as well. The...
    view full answer...
  • Can Trailer Brake Magnet Wiring that is Red be Ran to Wiring that is Yellow
    The great thing about trailer brake magnet wiring is that the wiring isn't polarity specific. That means that either wire can be used as power or ground as long as opposite wire is connected properly. So it doesn't matter which wire you run to your magnet wire by color as long as the other wire is connected properly.
    view full answer...
  • Gauge of Wiring in 35 Ft 4-Way Trailer Wiring Harness # A35W42B
    The gauge of the wiring in the 4-way kit part # A35W42B is 18 gauge.
    view full answer...
  • Installing 4-Way Connector on Trailer with 5 Wires
    If you have 5 wires on your trailer and a 4-pin connector, you most likely had what is called a wishbone harness on the trailer like # A35W42B. On a wishbone harness, you will have two wires attached to the running light circuit because there is one wire for each side of the trailer. I recommend testing the wires on your trailer with a 12V battery so you can verify each of their functions. Going by color alone is not the best method, as manufacturers and aftermarket wiring can change...
    view full answer...
  • Where Does Red Wire of 4-Way # 62990 Wire To on Trailer
    While we do not carry the 4-way kit part number 62990 I can tell you how it wires up. Basically the harness is a wishbone 4-way which has two wires for the running light circuit. One for each side of the trailer. The red wire goes to one side of the trailer's running lights and the brown goes to the other. Doesn't matter which side you pick. We have a similar wishboned 4-way wiring harness as part # A35W42B.
    view full answer...
  • Where to Connect Trailer Brake Magnet Wires on a Tandem Axle Trailer Towed by a Ford F-350
    Electric trailer brakes have electro-magnets and they will need to be connected to the 7-Way trailer connector in order to receiver power from the brake controller in your Ford F-350. Since your truck is already set up with a brake controller and trailer connector we need to just focus on the trailer side. On your brake magnets one of the wires will be the power wire and the other will be the ground. It does not matter which is which. The ground wires should be attached to clean and corrosion...
    view full answer...
  • Which Wire of Trailer Brake Magnets Gets Ran to Power and Which to Ground
    The great thing about trailer brake magnet wiring is that it's not polarity sensitive which means that either wire can be used as the power or the ground. So as long as one of the wires on your trailer is power for the brake output circuit and the other is ground it would not matter which would attach to which on the magnets as long as the other wire matched correctly. I attached a link to a page on trailer wiring with diagrams for you to check out as well.
    view full answer...
  • Is the Optronics 35 Ft 4-Way Trailer Wiring Harness Wire 100 Percent Copper
    I reached out to Optronics and they confirmed that the wire used in the 35 Ft 4-Way Trailer Wiring Harness - Wishbone Style # A35W42B is 100% copper. This harness comes with 2 tail light wires split for simple wiring and has a 3 year warranty.
    view full answer...
  • Running Light and Reverse Light Circuit Not Active on Ford F-150
    It sounds like you have narrowed down the issue to the truck considering you do not have the same issues when hooked up to another tow vehicle. The first thing you want to check is the ground on the 7-way of the truck to make sure it is properly grounded to a clean bare metal surface on the truck's frame. I am assuming the actuator on the trailer has an electric lockout that allows you to back up with hydraulic brakes. For the electric lock out to function properly, you need a working...
    view full answer...
  • Wiring Stop Turn and Tail Light Circuits to a Trailer Light
    Your trailer lights should only have one wire if the light serves only one function (tail light, marker light, stop/turn). The white wire shown in the photo that you attached is a ground wire and will not be connected to the tail light or stop/turn circuits. The bulb attached to your light housing looks like an 1157 bulb, which is a dual filament bulb that has two contacts for two different circuits. You should have two wires on the back of the light housing, one for the stop/turn circuit...
    view full answer...
    Image 1 for
  • Trailer Wiring Replacement Recommendation for Trailer that Has 4-Way and 5 Wires
    Sounds like your trailer has a wishbone 4-way installed on it which means that two of the wires go to the same circuit (running lights) and the rest run to individual pins of the 4-way. For that we have the part # A35W42B which is 35 feet of wishbones 4-way for you to use to replace what you have. The two brown wires run to both of the running light pins of the connector you have. Then the rest wire where they need to go. If you are unsure where each circuit goes on your trailer's wiring...
    view full answer...
  • How to Wire Second Axle of Trailer for Brakes
    Yes, you can jump the front axles brake output circuit to power the rear axle. Check out the picture I attached to see how most people do this.
    view full answer...
    Image 1 for

Do you have a question about this Trailer Wiring?


Info for this part was:

Employee Mike L
Expert Research:
Mike L
Employee Robert G
Expert Research:
Robert G
Employee Michael H
Expert Research:
Michael H
Employee Jameson C
Expert Research:
Jameson C
Employee John H
Expert Research:
John H
Employee Adam R
Expert Research:
Adam R
Employee Rachael H
Expert Research:
Rachael H
Employee Jeffrey L
Expert Research:
Jeffrey L
Employee Victoria B
Expert Research:
Victoria B
Employee Zack K
Video Edited:
Zack K
Employee Brian T
Updated by:
Brian T
Employee Carrie F
Updated by:
Carrie F
Employee Sabrina W
Updated by:
Sabrina W

At etrailer.com we provide the best information available about the products we sell. We take the quality of our information seriously so that you can get the right part the first time. Let us know if anything is missing or if you have any questions.