B+ Wire From 7 way Connector

[Metroretiree]

I am in the process of installing a Victron 30 amp DC to DC charger and 300AH of Li batteries. I need to identify where the 12VDC B+ wire goes to after leaving the junction box at the king pin. I have searched for prints to no avail. After retiring as a electromechanic for 32 years I know the value of having a road map to what you are working on. The rig is a 2021 3791RD 5th wheel. Thanks.

[firestation12]

Yours is a question that has been asked numerous time. The only information provided is the color coding for the low voltage circuits. Keystone offers nor help in terms of a schematic. The termination point of the B+ wire you’ve located at the pin box j-box will likely be on your battery or one of the automatic resets located near the battery and are attached to a vertical surface. I’d suggest looking for a wire the same gauge and color as the J-box contains. Should be a 10ga. A line tracer would help you, or simply disconnect suspected wires and see if voltage is lost at J-box. If you were to expose the backside of the front/side storage compartment and were to see the rat’s nest of wiring that Keystone employees fail to trim to length, rather they leave it in a twisted pile, you’d understand why there is no schematic. Each camper is like snowflakes….no two are alike. It is what it is, as the saying goes.

[Daryles]

When I installed my DC-DC charger, I left the 12vdc charging wire coming from the truck intact.

https://www.montanaowners.com/forums...hlight=charger

[Lee-CI]

Originally Posted by Daryles

When I installed my DC-DC charger, I left the 12vdc charging wire coming from the truck intact.

https://www.montanaowners.com/forums...hlight=charger

Like Daryles, I left mine intact as well. With my Renogy DC-DC charger, I ran a 16 AWG "ignition wire" through a SPST switch mounted in the front bay near my charger. I use the switch to turn on the charger when I need it while traveling. For the most part I followed the road map in the link provided above so as not to have the need to re-invent the wheel. Setup has worked flawlessly for us. Good luck with your installation.

[Metroretiree]

Thanks all for the info. I have worked on the following equipment in order, helicopters in the Navy, small engines, and subway trains. ALL had repair manuals, even the small engines. I can not understand an industry that does not have their cost nailed down with a small amount of standardization enough to produce a manual. I will try to find a trail of bread crumbs. This will turn a job that should last a few hours to days. Enough, off my soap box. Will remember as I make my next payment. Thanks again.

[Daryles]

20 years working on Naval jet aircraft. Another 20 in IT.
A wire tracer (dog and bone) works great.
Klein Tools VDV500-820 Cable Tracer with Probe Tone Pro Kit for Telephone, Internet, Video, Data and Communications Cables https://a.co/d/6k9BcoS

[MandK]

Originally Posted by Metroretiree

I am in the process of installing a Victron 30 amp DC to DC charger and 300AH of Li batteries. I need to identify where the 12VDC B+ wire goes to after leaving the junction box at the king pin. The rig is a 2021 3791RD 5th wheel. Thanks.

Just noticed this thread, I might be able to add.
Below are a couple pictures. The j box photo is from when I was doing my disc brakes. The crimp I marked 12 v with the black (from truck) to red (coach) runs through the loom that runs from the pin box down the ods of the overhang, through the propane compartment and into the battery bay. The loom is marked by the red arrow in the second picture. It comes out of the loom and is the 10 ga red shown attached to the terminal shown by the yellow arrow. You could shut off the power and pull the connection and check for continuity to see if both of our 2021’s are the same.

[Metroretiree]

Thanks for the info. The wheel has been invented. Just need to improve. I had the wire at the junction box going from black (7 way) to red (camper), then lost it after it went into the loom. Info is timely, I am about ready to start the job this morning. I will post photo's after completion.