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Trailer Wiring Junction Box

Trailer Wiring Junction Box

Item # 38656
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Spectro Accessories and Parts - 38656
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This Spectro trailer wiring junction box provides a fast, easy way to connect the wires from the trailer connector to the wiring for either a 6-way or 7-way connector. Makes replacing your trailer's connector simple. 1-800-496-5010 to order Spectro accessories and parts part number 38656 or order online at Free expert support on all Spectro products. Great prices and Fastest Shipping for Trailer Wiring Junction Box. Accessories and Parts reviews from real customers.
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Spectro Accessories and Parts - 38656

  • Trailer Wiring
  • Junction Box
  • Spectro

This Spectro trailer wiring junction box provides a fast, easy way to connect the wires from the trailer connector to the wiring for either a 6-way or 7-way connector. Makes replacing your trailer's connector simple.


  • 7-Terminal junction box lets you easily connect your trailer wiring to a 6-way or 7-way trailer connector (sold separately)
  • Weatherproof, heavy-duty plastic protects wires and terminals from the elements
  • Mounting hardware included
  • Ring terminals (44-5310A) sold separately


  • Box dimensions with lid: 7" long x 3-1/4" wide x 2-3/4" tall
    • Overall length (with mounting flanges): 8"
  • Distance between mounting holes (on center): 7-3/8"
  • Mounting flange dimensions: 3/4" wide x 1/4" thick
  • Outer diameter of terminals: 3/16"

9709 Spectro Trailer Wiring Junction Box

Video of Trailer Wiring Junction Box

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

Video Transcript for Spectro Trailer Wiring Junction Box Installation

Today were going to install part number 38656. This is a trailer wiring junction box. First thing were going to do is find the location for our junction box. Were going to go ahead and install on the inside edge of the tongue. Well go ahead and hold it up to the tongue and then well go ahead and use a drill to mark it for our holes. We have our holes marked, well go ahead and remove the box, and then go ahead and drill out our hole.

Now well go ahead install our hardware and install our box. Now were going to use a quarter inch hardware to install the box to the frame. This hardware does not come with the box. With our box installed, we can go ahead and start getting our wiring ready. Well go ahead and cut our wires to the length of what we need and then well take our excessive length from our gray cable and use the white wire for our ground lead.

Were going to take the white wire, well add a couple of ring terminals, and well go ahead and connect it to the post labeled white and ground. Well also change out one of solid grommets for a hollow ground. With our new grommet installed, well go ahead and fish our wire through, and attach it to the box, and then were going to use a self-tapping screw to attach it to the frame. Now well go ahead and get the rest of our break cable ready, the gray cable will be for our electric brakes. Well cut back the gray sheath to expose our two wires.

Our white wire will go to ground, our black wire well go ahead and post to label blue, blue is only the function for brakes. Well go ahead add some ring terminals to it, then temporally put them into position. Now well go ahead and hook up our wires for our trailer lighting, well also go ahead and run it through the grommet and then go ahead and install our ring terminals. Now the brown wire on our trailer will be even running light circuit that will go to the post labeled brown, it will also say taillights on there. The green wire will be our right turn signal, well go ahead and connect that wire to a post labeled green, and it will say right turn.

The yellow wire well be our left turn signal and that will be connected to post labeled yellow and left turn. Now these wires have been loosely installed. Next well go ahead and wire our trailer connector, this is going to be a seven molded trailer wire connector, eight foot long, part number h20046. You see the seven pole and we have our wires. Once thing to know about this is that the functions do not match the colors better on the trailer. Now on the other side of the box well go ahead and replace them with solid grommets with a hollow grommet and well go ahead and run that over our wire that we can go ahead and push the wire back into the box. Then well go ahead and add our ring terminals to our wires. Now well go ahead and start attaching our wires, well start off with the green wire from the seven-pole which will be our running lights; this will be connected to the post with the brown wire from the trailer lights. The brown wire will be our right turn so that it will be connected to the post with the green wire from the trailer lights. The red wire will be the left turn function on the seven-pole, so well connect that to the post with the yellow wire from the trailer lights. Our blue wire will be our brake control power, so well hook that up to the post labeled blue. Now our yellow wire is usually reserved for reverse light or whatever function youd like. However, this application is not being used, so well just ignore that wire. Our black wire will be our 12 volt power supply, however this trailer is not using it right now, but well keep it to the junction box for our upgrade in the future. Well now go ahead and take our white wire push it to the ground from our towing vehicle that will be transferred to the trailer and well connect that back up to the white post, well get two white wires. With all of the wires in place well go ahead and tighten down the nuts. Next well go ahead and install the clamp from the wires that come in from the trailer side. Looking at the box on the left hand side there is provision for a clamp. Well make sure everything is pushed together properly and wont get pinched, well go ahead and install the cover. Well fasten and replace of these two bolts. Thats what it takes to install our junction box. All right with that it will finish it for our install of part number 38656, a trailer line junction box on this new trailer.

Customer Satisfaction Score:

Customer Reviews

Trailer Wiring Junction Box - 38656

Average Customer Rating:  4.8 out of 5 stars   (723 Customer Reviews)

This Spectro trailer wiring junction box provides a fast, easy way to connect the wires from the trailer connector to the wiring for either a 6-way or 7-way connector. Makes replacing your trailer's connector simple.


I needed a way to reorganize wiring for my very old utility trailer. This wiring junction box from etrailer met my needs exactly and made my re-wiring project easy

It works well to organize wiring.
Dale P - 07/14/2022


perfect to make a universal trailer hook-up, Hi quality parts, see adjacent review for completed assy


The junction box is well made and provided all of the posts needed to connect the 7-pin wiring that I used while restoring my 1969 Gold Star travel trailer


This junction box was exactly what I needed. Had a short from cable wear and needed to splice on a new pigtail. This box made it super easy and really clean.


First things first. Love your company! Keep up the great work. etrailer has been my go to site for all my trailer needs. As for the break away kit. I got a used inclosed trailer and it had a very large truck battery inside the trailer with a very large hole in the floor for the trailer breakaway system. An eye sore to say the least and very much in my way. I was shopping around etrailer site found the Bright way breakaway system. Watched the review about it. Did not think it would work for my two axle brake system. Ordered it anyway. Installed on outside of trailer. Did all this after installing new brakes. Did a test and I could not get the wheels to turn with trailer off the ground as well as doing a test with the trailer on my truck and the breakaway system worked and held the truck in place. Bottom line is the system does it job for a small battery. Love the system. It is small, can be placed almost anywhere, and again does its job. Only issue I had with it was the two screws that hold the cover closed started to rust after the first time it got wet. I replace them with better ones.


just got items this morning. Did not give 5 stars because they sent my items to my billing addresswhich is a local post office. I live in a rural area aand have packages sent to residence UPS/FEDEX. I have to drive 10 miles to pickup US AIL items. NOT convenient and some times a deal breaker for me.


I was able to replace a residential electrical box with this Junction Box. The residential box was mass of wires with wire nuts that are not suitable for a 5th wheel trailer. Also, it was almost impossible to track wires when troubleshooting an electrical issue. It is a shame that Forest River would build RVs that could become such a dangerous situation if wires become lose(i.e. Brakes, etc.). Wire Nuts are not to be used in an environment subject to vibrations . I cam now trace my wires with ease, if needed.

Since I installed this box, I have not had any issues with brakes, lights or charging systems from the truck or 5th Wheel Trailer. I am very happy with the results.
BBMUSE - 02/08/2022


I’m a one bay, one man operation and I see my customer nearly every week and he is still super satisfied with the brakes. While installing them the quality of the product very evident! I have a smaller trailer that I probably don’t need brakes on but if I decide to I’ll definitely be ordering the set from you all!!!


This box was used as part of an electric brake conversion on my trailer. This box was an excellent means of connecting the existing wiring and the new brake wiring into the new 7 way trailer connector. It has the required breakouts and grommets needed to make the wiring task the easiest part of the conversion.

For a neat install and ease of replacement later if necessary, theres no better way to go than a junction box.
-- Etrailer Expert Mike L - 07/25/2019
Im very satisfied with this connection box. It keeps all of the connections well insulated and out of the weather.
TomD - 07/24/2020


It is going to serve the intended purpose of gathering all these wires into a controlled location. The only drawback is the labelling on the box for the wire locations is extremely difficult to read. Not a big deal.


Installed in about 30 minutes, made install a breeze and took the mess out of a rats nest of wiring spliced under the trailer. Comes with plenty of grommets and all hardware to put together. You need to supply the bolts or screws to mount this to your trailer. Each terminal is labeled for what connects to it taking the guess work out of matching wires up.

Still works great, no issues at all.
Richard P - 10/14/2018


Had to replace my 7 PIN plug and found the old one was crimped onto the trailer wires, URGH. So trimmed all the trailer wires and terminated them in this box. Made connecting my new plug much better.


This is my second purchase of this product. I actually have now purchased a third one. It’s a great way to hook up a new pigtail to existing wiring.


Rewired my trailer and used this junction box to go from my main cable to all the individual lights and brakes. It worked great, the only thing I didn't like about it was that it only had two cable clamps on the inside

I still have all the electric supplies from etrailer on my cargo trailer. I have had no issues with any of your products whatsoever. I hope this helps
Chris B - 11/11/2017


Exactly what I needed to clean up the rats nest that came on my camper. Now its clean, neat and less likely to give me problems down the road Great customer service and fast shipping


Simple easy and effective. This isn't the first time I've used this style of junction box, but they definitely make wiring any size trailer soon much easier.


Excellent product and customer service. I have been using e trailer for years and they haven't steered me wrong yet.


I purchased this product after researching current trailer rewiring methods. I recently had my entire 18' trailer wired and upgraded. The trailer is 8 years old and I wanted to replace the original 4 way trailer harness which the trailer manufacture had surrounded in electrical tape which also needed an adapter. After some research, I opted for this 7 way pigtail (50-67-005) which is the connector I needed my trucks and this junction box. (all contacts were current)
The junction box is sturdy and well made, we installed 7 way wire within the box with a snug fit. The trailer now has a clean professional appearance and most test functions can be performed from the junction box location. The junction box was installed behind the trailer tongue frame to minimize the weather elements. This product appears to seal well as the product description indicates. I am very satisfied with this product and Etrailer's customer service.


Now I have a chuckwagon that is all tricked out for side marker lights and more. This box really did the trick for keeping wires organized.


We wanted both a 7-wire and a 4-wire plug on the same trailer. This junction box made the installation very easy. If your connecting the Hopkins 7-wire harness to this box, you'll probably have to ignore the wire colors names and just use the location (R Turn, etc.). Both are marked on each terminal.

There are 5 different openings to choose from to route the wiring to this box and it comes with both rubber grommets to run wiring through and rubber plugs for the openings not used. A downside is that only the side with 2 openings has wire hold downs on the inside. It would have been nice if at least the opening on the opposite end also had such a feature.

It's fairly water tight and installed easily onto the frame, under the trailer. Because it's lightweight plastic, I'm not so sure how long it'd last in the direct sunlight if it was mounted on the tongue or other exterior location.


Junction box was perfect for my applica tion...thanks.....


This trailer was built from scratch using only the metal frame. I purchased some items from etrailer an was very satisfied with the products.

Great job! Looks like a high quality build.
-- comment by: Mike D - 03/26/2015
Its still working great.
Wayne M - 08/07/2015


Installed as I had planned and it went well. Wired the supply line to the box to all of the correct wiring terminals as it is labeled in the box. I was prepared by other reviews, things may not match up, which they didn't, but no biggie. Once I flipped a few wires around things worked nicely.


I love these boxes. I've repaired numerous trailers my sons and I own, including cargos, flat beds and horse trailers. I really like the grommet locations, cable clamping and posts for wire connections. There is plenty of room inside to neatly route wires.


Handy place to splice wires especially if you need to isolate trouble in the future.

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