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HOW TO: Junction Box for the 7 Wire Trailer Harness, under the front dinette seat

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Here is a related thread, I installed a similar box up front under the jack: ... https://olivertraveltrailers.com/forums/topic/2688-how-to-junction-box-for-trailer-harness-repair-or-extend-the-harness/

This all came about because I wanted to install a ...  Redarc DC to DC Battery Charger .... and I needed to know FOR SURE that the wires were big enough. 12 AWG is the absolute minimum according to Redarc, and bigger is always better, especially in an Ollie with a very long run back to the batteries. Here are the existing butt splices, half of them are absolutely buried under the sewer pipes. Time for a J-Box!




So I cut all the splices, and dragged the ends up to where I could inspect the wires. Most were OK, but the white Ground wire was not. Somebody extended the front wire with a smaller sized one. Darn it!


I bolted down the box next to the 120 VAC outlet. I spliced into the green and white running light wires and brought them up to the box via the bottom hole. The other wires come in from the left and right sides. I ran heavier 10 AWG black and white wires (power and ground) from the box back to the appropriate posts. So now the Redarc charger will not suffer from excessive voltage drop, and with the easy access, it will be very simple to troubleshoot any future 7 Wire Harness problems.



The new splices are easy to ID because they have clear spiral wrap plastic, and they are secured to the inside wall using a 1" thick block of HDPE plastic, bonded with JB Weld directly over the small LED light.




The placard goes inside the J Box using 3M double stick tape.


Here is the placard, in  Apple Pages format:

Oliver Junction Box wiring placard Rear 7 pin.pages

Note that I indicated where those marker light splices are - I hate not knowing!

John Davies

Spokane WA





Edited by John E Davies
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SOLD 07/23 "Mouse":  2017 Legacy Elite II Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 32” LT tires, airbags, Safari snorkel, Maggiolina Grand Tour 360 Carbon RTT.

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  • 1 year later...

Yep, found it now!  🙂

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TV:  2019 F-150 SuperCrew Lariat, 3.5L EcoBoost, Max Tow, FX-4, Rear Locker      OLLIE:  2018 OE2 Hull 342, Twin Bed.    OLLIE DIY’s: Timken Bearings, BB LiFePO4's, Victron 712 Smart, 350 Amp Master Switch, Houghton 3400, Victron Orion DC - DC, 3000-Watt Renogy Inverter, P.D. 60-amp Converter, Frig Dual Exhaust Fans, Kitchen Drawer Straps.    TV DIY’s:  2 5/16" Anderson System, Nitto recon’s, Firestone Rear Air Bags, Bilstein 5100’s, Mud Flaps & Weather Tech all, installed Ham Radio (WH6JPR).







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Very clean - nicely done!

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Art, Diane, Oscar & Magnus (double-Aaarrf!)

  • 2022 TUNDRA w/Airlift Load Lifter 5000 kit/2017 LE II; Hull #226 "Casablanca", 12VDC Starlink kit, 3x Battle Borns; Victron Cerbo GX, SmartShunt, MPPT Solar Controller, & DC-DC Charger; HAM call-sign:  W0ABX
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