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Rewiring a trailer can be a daunting task, but the unique wishbone design of this 40 Ft 5-Way Trailer Wiring Harness makes it straightforward. With separate wires for each tail light running down the length of the trailer, there's no need for a jumper wire. This smart setup allows you to easily split the tail light circuits, saving you time and hassle.
Ever had trouble with your trailer brakes engaging when backing up? The harness' auxiliary wire is a game-changer. Connecting to your trailer's backup light circuit, it efficiently disengages hydraulic or surge brakes, making reversing smooth and problem-free. If your actuator has an electric lockout feature, this harness is exactly what you need.
Struggling to find a harness long enough for your trailer? This one spans an expansive 40 feet, catering to larger trailers or intricate setups. It's ideal for marine trailers and those tougher, more challenging trailers where a little extra length makes all the difference.
Forget the uncertainty when wiring your trailer for lights. This wiring harness is color-coded, making installation straightforward and user-friendly. With intuitive color guides like white for ground, brown for tail lights, and more, you can set up your trailer lights with confidence and ease.
Looking for a wiring harness that can stand up to challenging conditions? This trailer wiring harness is durable, designed to reliably control your trailer light functions for the long haul. Whether towing a boat trailer or a utility trailer, its robust design is made to meet the demands of regular usage.
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Very fast shipping.. Looks like its gonna be a breeze to install..
Quick shipping and easy use of web site for ordering will reuse again
Excellemt product and service as always. Etrailer is the best source for your products . They have outstanding service and pricing.
Design wise it is excellent, the wishbone design is intelligent and makes rewiring a boat trailer simple and clean.
The Good rating? The wire gauge looks to be 18-20, wish it was heavier gauge, especially since it is a 40 ft long harness. And it is made in China or Taiwan, not a heavy duty or perfect construction.
If it lasts as long as my original, 14-years, I'll come back and bump up my rating, and I bet you can't find a better one.
As far as the transaction, it was excellent, had the 40 footer I needed, great price and super fast shipping.
I would have to give my representative Madison 5 stars as she was very pleasant and helpful. I overall gave this product as a 3 mainly because the ground wire is so short as my preference is to ground each light back to the vehicle rather than the trailer frame and I have backup lights so the backup (blue wire) should be considerably longer so as to reach the furthest backup light.
After years of use of the original wiring harness on my boat trailer, it was in need of replacement. This new Optronics harness was definitely the thing it needed. It fits perfectly, with minimal modifications, to make it work. All the corroded connectors were replaced and now the lights work again!
The wiring harness arrived on time and in perfect condition. It's a very simple product but worked exactly as it should. Got all my trailer lights working now.
If your trailer has more than a couple running lights along with your tail light, this harness will not work well at a 40ft length with this gauge wire.
My boat trailer had a split wiring harness that had suffered over the years. I purchased this harness for the boat trailer and with attaching it to the old wire was able to pull it through the frame and connect all new lights in an afternoon.
Good product and always works
Great product
Russell 
4/26/2024
Great still wirking Good
It should work
I guess I should of read discription better , wire harness delivered had 4 wires that were 30’ in length , but the blue and white wires were only 36” in length , I had to go out and but a roll of white and a roll of blue to complete replacement PU camper break circuits.
Jenny N.
1/31/2022
This harness comes with 40 foot of the brown, yellow, and green whites. It comes with 30 foot of the white ground wire and 5 foot of the blue auxiliary wire. The auxiliary wire connects to backup light circuit to disengage surge brakes when you are driving in reverse. The hydraulic actuator must have electric lockout feature built-in to disengage the trailer brakes
This harness worked well for my 21 foot boat trailer. There was excess wire and it took care of some corrosion problems I had with my old wiring.
Etrailer always has great descriptions so you know what is being shipped.
I got my 40ft wishbone trailer harness in about 5 days. Was held up a day because of the Christmas holiday. All in all I was quite satisfied with my purchase. I'm putting "Pole Lights" on my trailer to keep them out of the water. I didn't want to "splice any wires", so I ordered the 40ft length. I have not yet installed this, but plan to start today. Its been a very busy holiday season, and now time to get to work.
Capt. Jim Hedgecock
THE PRODUCT CAME QUICK AND ETRAIER AS THE ONLY PLACE TO HAVE THIS PRODUCT. 40 FT TRAILER HARNESS . WE WILL BE INSTALLING IT ON MY 2010 CONTINENTAL BOAT TRAILER . FILMING IT ON MY YOUTUBE CHANNEL . .SHALLOWHOOKERFISHING.COM . ILL BE HAPPY TO MENTION ETRAILERS.COM ON MY CHANNEL. .
etrailer is a the only place I could find this item as I live in a rural area. The harness was perfect and did the job well. Service and shipping time was perfect.
The harness seems fine but receiving this item from etrailer was terrible. I didn’t have enough in my cart for free shipping so I was charged, which is fine. What I am not fine with is etrailer using the pony express to get it to me. If I can find it on [online vendor] I will get it from there.
Very satisfied with product. Only recommendation is charge an extra minimal amount for splices, terminals and etc.
In my DIY application, replacing the bumper plug connector. I'll retain the remaining wiring harness for near future replacement.
Excellent wiring harness!! Hasn't given me any trouble in over a year.
Exactly what I was looking for and fast delivery.
Completely rewired my trailer and this kit had all that I needed.
Great experience! Good product and fast delivery.
My 5 pin, 40' wire harness arrived within just a couple days. Excellent price and Excellent service. Thank you etrailer.com.
Great Quality. This harness has 20ga wire. wish the wire gauge was thicker. I used this for a boat trailer rewire and 16ga would beef the harness up perfectly.
Do you have a question about this Custom Fit Vehicle Wiring?
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Brooke M.
3/24/2025
Madison is awesome for sure! I will make sure she receives your message :) I appreciate your honesty on this part as it pertained to how you prefer to install the ground. I'm sure there are others out there who share your opinion and this will be helpful to them, too :)