Junction Box under Travel Trailer

[HistoricMustang]

Ran across this junction box under my new Forest River "Salem" FSX 177BH while doing some extra "hole plugging" with foam sealer.

It is located just behind the hitch.

Can I assume it is related to charging battery while camper is hooked to tow vehicle?

Thanks in advance.

[nic7320]

Looks like there might be some electronics in there. I see a thermal circuit breaker for the two big red feed wires, which are most likely your battery charging lines, and power from that going into the box through the blue fuse holder. Then several wires leave the box, so those might be feeding your electric brakes, or any number of other things. That box is a standard j-box for house and industrial electrical wiring, and it isn't waterproof for exterior use. I would seal that up with a better cover plate and put some putty around the wire exits.

[HistoricMustang]

Originally Posted by nic7320

Looks like there might be some electronics in there. I see a thermal circuit breaker for the two big red feed wires, which are most likely your battery charging lines, and power from that going into the box through the blue fuse holder. Then several wires leave the box, so those might be feeding your electric brakes, or any number of other things. That box is a standard j-box for house and industrial electrical wiring, and it isn't waterproof for exterior use. I would seal that up with a better cover plate and put some putty around the wire exits.

Thanks. Will get my trusty tube of silicone sealer.

I assume the red wires are not ground wires and have "live" 12 volts.

[chriscowles]

Originally Posted by HistoricMustang

Ran across this junction box under my new Forest River "Salem" FSX 177BH while doing some extra "hole plugging" with foam sealer.

It is located just behind the hitch.

Can I assume it is related to charging battery while camper is hooked to tow vehicle?

Thanks in advance.

Note that the trailer umbilical cord comes in the front end. Connections to running lights, tail lights, brakes, and power to various points in the trailer exit out the back.

This is the one on my Rockwood Mini-Lite. Yours is approximately the same. They vary somewhat by manufacturer and installed options. The 20A Type I (auto-reset) breaker serving the slide-out and tongue jack is mislabeled 30A. I have since added backup lights, connected to the yellow wire.

The CO/LP alarm and slide-out power wire pass through the box without connection. The slide-out connects to the 20A Type I breaker and the CO/LP alarm goes to the disconnect switch. The manufacturer puts it on the hot side of the switch; I moved it to the switched side.

[HistoricMustang]

Originally Posted by chriscowles

Note that the trailer umbilical cord comes in the front end. Connections to running lights, tail lights, brakes, and power to various points in the trailer exit out the back.

This is the one on my Rockwood Mini-Lite. Yours is approximately the same. They vary somewhat by manufacturer and installed options. The 20A Type I (auto-reset) breaker serving the slide-out and tongue jack is mislabeled 30A. I have since added backup lights, connected to the yellow wire.

The CO/LP alarm and slide-out power wire pass through the box without connection. The slide-out connects to the 20A Type I breaker and the CO/LP alarm goes to the disconnect switch. The manufacturer puts it on the hot side of the switch; I moved it to the switched side.
Attachment 252813

Thanks for the help and information.

- HistoricMustang

[D W]

A "typical" J-Box will be configured like this:

[TitanMike]

Originally Posted by HistoricMustang

Ran across this junction box under my new Forest River "Salem" FSX 177BH while doing some extra "hole plugging" with foam sealer.

It is located just behind the hitch.

Can I assume it is related to charging battery while camper is hooked to tow vehicle?

Thanks in advance.

This box is where the various lights, Tail, Brake, Clearance, are connected to the cord connecting your trailer to the tow vehicle. Also includes brake wire and backup lights (if equipped). The 12 volt charge wire and battery connection to power center pass through the small circuit breaker.

Because this box is a residential type J-Box and not designed for use in wet environment it was one of the first things I replaced on my TT. Here's what my setup looks like now:



This "box" and circuit breaker are the source of most complaints where batteries aren't charging, no 12 volt power in trailer when not hooked up to shore power and tow vehicle is not connected. That's why I chose the pictured box which is used on many commercial trailers for both water resistance and to minimize maintenance/repairs.

Fairly inexpesive and can be obtained for less than $10 on Amazon



I went 'deluxe' and put crimped ring connectors on the end of each wire so connections were positive.

As for the circuit breaker, I hate the factory type so I installed a waterproof one with a lever that shows more easily when it's tripped instead of the small, almost hidden, button. Also easy to reset as well as "trip" if you want to use it as a shutoff.

[SetauketJeff]

Amazon Trailer Terminal Junction Boxes:
https://www.amazon.com/MICTUNING-Way...9375815&sr=8-5

https://www.amazon.com/Dumble-Electr...375815&sr=8-31

[Thurman]

I'm sure someone will correct me on this IF I'm wrong but my years of electrical experience kicked into gear in my brain and told me that under the NEC (National

Electrical Code) it would be illegal to "seal" that type of junction box with any type of sealant such as silicone. A rubber/foam gasket between the box body and the cover might be permissible, I'd have to look that application up again. That type of electrical junction box is very common on travel trailers and fifth-wheels.

[lwbfl]

Replacing that box seems like a great idea and I'm not sure why I haven't done so on any of my TT over the years. I've never had an issue with any of them but it seems like good insurance.

[HistoricMustang]

Thanks for all the help and suggestions.

- HistoricMustang

[SetauketJeff]

Originally Posted by HistoricMustang

Thanks for all the help and suggestions.

- HistoricMustang

We'll even help Ford guys!

[chriscowles]

Originally Posted by TitanMike

This box is where the various lights, Tail, Brake, Clearance, are connected to the cord connecting your trailer to the tow vehicle. Also includes brake wire and backup lights (if equipped). The 12 volt charge wire and battery connection to power center pass through the small circuit breaker.

Because this box is a residential type J-Box and not designed for use in wet environment it was one of the first things I replaced on my TT. Here's what my setup looks like now:



This "box" and circuit breaker are the source of most complaints where batteries aren't charging, no 12 volt power in trailer when not hooked up to shore power and tow vehicle is not connected. That's why I chose the pictured box which is used on many commercial trailers for both water resistance and to minimize maintenance/repairs.

Fairly inexpesive and can be obtained for less than $10 on Amazon



I went 'deluxe' and put crimped ring connectors on the end of each wire so connections were positive.

As for the circuit breaker, I hate the factory type so I installed a waterproof one with a lever that shows more easily when it's tripped instead of the small, almost hidden, button. Also easy to reset as well as "trip" if you want to use it as a shutoff.

Mike, you keep coming up with new jobs for me to do.

[TitanMike]

Originally Posted by chriscowles

Mike, you keep coming up with new jobs for me to do.

Read part of my sig line that says you never grow old when you keep finding new things to do. [emoji16]

[campers302]

Originally Posted by HistoricMustang

Ran across this junction box under my new Forest River "Salem" FSX 177BH while doing some extra "hole plugging" with foam sealer.

It is located just behind the hitch.

Can I assume it is related to charging battery while camper is hooked to tow vehicle?

Thanks in advance.

OMG Nice water proof box.

What in the world is FR thinking when they build these things.


Good luck with that.

[TitanMike]

Originally Posted by campers302

OMG Nice water proof box.

What in the world is FR thinking when they build these things.


Good luck with that.

FR is thinking "waterproof connection box=$10, residential box=$1.25."

What was the question again? [emoji1787]

[chriscowles]

Originally Posted by TitanMike

FR is thinking "waterproof connection box=$10, residential box=$1.25."

What was the question again? [emoji1787]

Realistically, how many have a failure related to those connections, out of the thousands on the road? The breakers do fail but only after many years.

[TitanMike]

Originally Posted by chriscowles

Realistically, how many have a failure related to those connections, out of the thousands on the road? The breakers do fail but only after many years.

On this forum alone I've read numerous posts regarding lights that don't work, brakes that are intermittent, and the problem is found inside this junction box. Usually loose or corroded wire nut connections.

It may not be a big deal with those who live in dry climates or never drive on wet roads.

[nic7320]

It's true that lots of trailers, particularly utility and boat trailers, have exposed wiring and splices hanging off the frame rails, and not in a box. But they fail a lot. It's sloppy and you would never get on an aircraft if it was wired that way.

The box protects the splices from water spray, grime, and mechanical abuse, and it limits vibration of the splices. I would just go two steps further. FIrst, seal up the existing box, and second, alter the brake wiring so its overcurrent protection device (circuit breaker) is located within the cab, and can be reset while driving.

There is no mandate to follow NEC. RVIA guidelines are for RVs, and sometimes have additional measures to deal with vibration. Case in point, wire nuts can be used in RVs if also taped with an approved electrical tape. Mind you, that's possibly one of the worst wire connectors you can have in a vehicle, and really should be avoided. High pressure crimp lugs and screw terminals are far better.

You really don't want your brakes to suddenly stop working.

[HistoricMustang]

Originally Posted by SetauketJeff

We'll even help Ford guys!

Ford folks need help with all the different engine packages through the decades. GM and Chrysler kept it simple.