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Battery-Trlr pigtail wiring fix and Upgrade

4X4Dodger
Explorer II
Explorer II
The last two days here in Bellingham WA I decided to tackle a project that I had wanted to do since I bought this trailer. The Battery cables and the Trailer/Truck Pigtail wiring were a total mess. All the grounds were corroded and the wire ends too.

A small metal household type junction box was mounted up under the trailer in front to house the connections between the trailer wiring and the pigtail and Battery. It was all put together with plastic twist on "Wire Nuts" used in houses. This is not unusual for trailers but should NEVER be allowed to my mind.

So here are some photos of my fix and how I think the wiring should be done. This is an easy job, any one an do it, the hardest part being sitting under the trailer to do most of it.

The first thing I did was make numbered labels to mark the wires before I took them apart to ensure I didnt cross wire anything. Then I cut each wire back a bit and terminated each with a high quality Ring lug terminal and them applied Heat Shrink to keep the weather and water out and reduce corrosion.



The next step was to install the Blue Sea Systems Power Bus Bar (rated for 150 amps) and the Distribution Block. These are very high quality Marine grade components that will outlive the trailer.



The big box you see is an 8" by 8" waterproof plastic enclosure I bought from Home Depot and cost about $22. Just cut the holes you need as I did.

Next I mounted a Blue Sea Systems Maxi Fuse holder for the 50 Amp fuse that was in one of those automotive type inline enclosures. The old fuse was a corroded mess and probably would not have tripped when it should have. The new holder is much stronger and the connection area much more secure and better contact. This was a bit expensive at $24.99.



Here is what the original Fuse and holder looked like: you can clearly see the corrosion which had migrated into the fuse itself



I then installed a weatherproof electrical outlet box around the Fuse Holder. Note the New Battery Cables which were also new and I terminated them with copper ring lugs and applied heat shrink.



Once all wired up, cables re-routed and dressed it looked like this:



I think this is an important mod anyone can do and it will pay real dividends if you have to track down a wiring problem in the trailer pigtail wires.

I also re-did all the ground points to the frame. I drilled new holes in the frame, cut the wires back to clean non-coroded wires and put on new ring lugs, wire brushed the frame to bare metal under the contact points and applied a dialectric grease (also available at Home Depot) to inhibit corrosion. This will insure very good grounding which is always the first culprit when trying to diagnose an electrical or charging issue.

All told the parts cost me a little over $100 but I think is well worth it. I hope it helps those of you who may be having problems with this area of your electrical system or those that just want to upgrade it.
12 REPLIES 12

Oldme
Explorer
Explorer
Very nice.
A well thought out upgrade.

4X4Dodger
Explorer II
Explorer II
Thanks to everyone for the nice comments. I didnt have to lay down on my back to do this my trailer is high enough that with the jack extended as far as possible I can sit up under there. Thank Goodness

And if you use the Blue Sea Systems Dist block and Bus Bar which is also very important you can add additional wiring very easily.

Lspangler
Explorer
Explorer
I used the 7 lug box also. When backed in my driveway my tongue Jack is almost fully extended to get the trailer level. With it that high I could sit on my but under the tongue and redo all the wiring.

Linc

bobndot
Explorer II
Explorer II
Very nice job, tnx for taking the time to post those pics, its very helpful .

rbpru
Explorer II
Explorer II
I discovered the same household type electrical box mounted to the front cross member of my frame. I had traced the break away circuit into it.

I remember thinking it looked like a poor set up. Fortunately when I opened it up the wire nuts and wiring were not corroded or damaged.

Though there was a lot of dust and dirt, their was no moister even though we have driven in a fair amount of rain.

I also remember thinking why didn't they mount it in the storage compartment directly above it and out of the elements? Oh well.

If had I needed to repair it I would most likely have soldered the twisted leads but I had bigger issues with the brakes at the time.

Thanks for pointing it our to the board.
Twenty six foot 2010 Dutchmen Lite pulled with a 2011 EcoBoost F-150 4x4.

Just right for Grandpa, Grandma and the dog.

_1nobby
Explorer
Explorer
I was just under there not long ago and have the same metal box with all the 12V harness, lights and main battery feed.

It was in surprisingly good shape.....but the bottom of my ttrailer is enclosed with coroplast....which, I'm sure, helps.

I might upgrade in the future but for now I need to start camping and work out the rest of the bugs.

hbrady
Explorer
Explorer
Beefie wrote:
What you folks did is the way they should come from the factory. Nice clean work on the installs. I have used the 7 lug terminal box in the past and it makes checking wiring a breeze now. Very easy to add more back up lights with one as well.


X10!
2015 RAM 2500 HD Crew Cab w/ 5.7L Gas
2018 SportTrek 290vik
Blue Ox SwayPro

myredracer
Explorer II
Explorer II
proxim2020 wrote:
The nut for the ground connections was rust welded and took quite a bit of effort to snap off. This was on a trailer that left the factory floor just 5 months prior.

I'm not sure why the industry still thinks that a junction box that's meant to dry locations in a home would be appropriate to install on the exterior of a trailer and at a pretty low point at that. They could at least us waterproof connections inside of the box.


One problem is the delivery of TTs during the winter when there is salt on the roads. Add that to the crappy wiring and exposure to water, things are gonna corrode.

Any electrical inspector or EE would reject wiring like this on a building project in a flash. It is bad, bad, bad IMO. Losing 12V lighting or appliances is one thing, but potentially losing TT brakes is a whole other matter.

myredracer
Explorer II
Explorer II
Excellent work! This is one mod that everyone should do. At the very least, it's definitely worth inspecting all the connections. What is the box mounted to? Looks like there's metal welded to the frame?
4X4Dodger wrote:
All told the parts cost me a little over $100 but I think is well worth it. I hope it helps those of you who may be having problems with this area of your electrical system or those that just want to upgrade it.
The worst part hasta be laying on your back for hours in a cramped position. ๐Ÿ˜ž
4X4Dodger wrote:
It was all put together with plastic twist on "Wire Nuts" used in houses. This is not unusual for trailers but should NEVER be allowed to my mind.
I could not agree more. All the manufacturers do it pretty much the same way. The wiring is supposed to be done to NEC requirements but it's not. Who would you contact to complain to??? I don't think there is any gov't dept. in the US to report to on RV electrical work. It's an accident waiting to happen in some cases.

I just did something similar. I'm an EE and am disgusted by how bad our wiring was. One of these days I'll post an in-depth "story" about what I found and did. Our 2 mini-breakers were a badly corroded mess. Several of the wire nuts were upside down and filled with water causing corrosion of the wires. Worst thing was the main positive #8 wire from the battery - the crimp type ring terminal at the breaker was barely crimped and the wire simply fell out of the terminal when I touched it. Very serious consequences if it fell out while towing at 60+ mph on a downhill stretch and you lose trailer brakes as a result.

Our manufacturer (KZ) did not wire the elect. stab jacks in accordance with Lippert's specs. They used #14 wire when it should have been #10 and did not install fuses (in addition to the breakers).

I mounted 2 mini-breakers, 2 fuses (for jacks) along with all splices in a watertight box and used 3/4" compression type PVC connectors. In my case, I soldered all splices and used a standard wire nut over them. I also added a watertight 12 VDC receptacle for our 12V compressor. A tight fit, but still all got in there okay. It is possible that water may collect inside the box due to condensation so I drilled a couple of small holes on the underside of the box. I installed a 2nd redundant ground connection from the battery to the frame for added reliability and safety. The 2nd pic is the main ground lug - badly corroded (in under 2 years), only 9 of 19 strands on one wire made it into the lug and I could not budge the screw at all.

The wiring to each of the brakes has light gauge wiring and the connections are of course suspect. Some day I'll take down the coroplast and upgrade it all but that's no Sunday afternoon project.

ps: Bellingham has the coolest hardware store ever, Hardware Sales. Very old school like out of the 1950s. I got the ring terminals and other bits there as they have a great selection.

Beefie
Explorer
Explorer
What you folks did is the way they should come from the factory. Nice clean work on the installs. I have used the 7 lug terminal box in the past and it makes checking wiring a breeze now. Very easy to add more back up lights with one as well.

trail-explorer
Explorer
Explorer
Very nice.

Lots of room to work in there.

I've seen pretty messy factory wiring jobs too: Wire nuts holding the stranded DC wiring together, in the same metal box your rig has.
Bob

Community Alumni
Not applicable
I second that this is an important upgrade you can do on a trailer. I did the same upgrade about a month back. I had plans to replace the box, but started having random loss of brakes before. Luckily my truck doesn't have a problem stopping the trailer on its own. I traced the problem back to the 7 pin junction box. I did a lot of traveling up north this winter on salted roads. The wire nut connections were all wrapped in electrical tape, but all of them had begun to rust. The nut for the ground connections was rust welded and took quite a bit of effort to snap off. This was on a trailer that left the factory floor just 5 months prior. I ended up replacing the whole box, replaced wire nuts for ring connectors, and heat shrinked the connectors. While I was there I went ahead and upgraded the brake wiring and connectors to 10 AWG.

I'm not sure why the industry still thinks that a junction box that's meant to dry locations in a home would be appropriate to install on the exterior of a trailer and at a pretty low point at that. They could at least us waterproof connections inside of the box.

This is the box that I used. It's a little cheaper and the studs are built in. However there's a tradeoff. It gets a little cramped in there because of the size and there's no room to include other items in the future. Good for those who are watching those pennies though. If I need to add more items then I'll move up to a box like yours.