Why was this done?

Discussion in 'Wiring' started by Bill R, Oct 21, 2019.

  1. Bill R

    Bill R New Member

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    Hello all,
    This site has been great in that I have repaired my lift system just by reading and learning from others with similar problems. Unfortunately my next repair/ problem I have not yet seen posted so here goes...
    Our NTU 1999 Coleman Taos has a four flat towing harness for the trailer lights.
    No battery, no 12V accessories except overhead lights and propane sensor. Our Magnetek converter works fine powering the 110 receptacles and converting 110 AC to 12 volt DC where needed. Here’s the question...at the four flat harness, a red wire is twinned with the brown wire sharing the brown pin.
    The red wire goes into the frame with the others. Exits the frame and is spliced into a black wire. Then the wires go into the trailer. Inside the trailer the black wire is spliced to the red wire which is in the back of the converter. Why the twinning of the red and brown. Would this be for charging a preexisting battery?
    To install a new battery would I just run a new wire to the red back at the converter?
    Thanks for the help!
    Bill
     
  2. tombiasi

    tombiasi Well-Known Member

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    Hard to say why they did it without seeing it. If you install a battery you will need a wire from the positive back to the converter. Your vehicle will not charge the battery with a four pin connector.
     
  3. rabird

    rabird Howdy!

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    Bill R, I assume someone did that so they could turn on the vehicle running lights and get 12v power for the ceiling lights, not the best idea!

    I'd get rid of the twinned wire at the 4 flat, put a ring terminal/inline fuse on it and hook it to a 12v batt + terminal, add a white wire from the battery neg terminal to a screw screwed into the trailer frame.

    or best yet wire the trailer/vehicle for 7 blade esp if ye ole taos has electric brakes!
     
  4. WrkrBee

    WrkrBee Well-Known Member

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    Flat four connector brown wire should be for tail and marker lights. That's a lot of splices in one wire. I assumed the same as rabird. Interior lights while connected to tow vehicle.
     
  5. Kerry L. Calkins

    Kerry L. Calkins New Member

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    Bill:

    I agree with Tombiasi.

    Something that I learned is that my trailer's 110v side is a bonded ground (meaning it is grounded from shore power source) and the 12v side is likely a bonded neutral (grounded to the trailer). Regardless of color, the wires that anchor to the trailer frame are neutrals or ground. Positive only connect to positive. Probably same for you. Not sure without looking at it.

    To charge your new battery from your Mag converter I needed to add a hot (+) wire from one of the converter's 12v output circuits (I used a line on a 20 amp breaker) to the battery positive (+). My Parallax converter has a designated 12v circuit for the battery and shares the same breaker as the external trailer running lights and door lamp. Tail lights and turn signals run off the truck lighting circuit.

    To charge from the truck while driving, you will need an additional wire from the truck alternator output to the battery positive (+). When I added my trailer hitch at U Haul, I had them add this charging wire as part of the the install of a 7 wire round plug truck-side connector/harness. You can either change your trailer connection to match the truck connector or use an adapter to connect the 4 wire flat to the truck connector. My Starcraft Comet PUP came with an 8 wire plug. So my adapter is 7 round to 8 stacked rectangle plug.

    I used to have a Magnetek converter. FYI, Parallax is the successor to Magnetek. My old Mag converter did not have circuits to transform the 110v to 12v to charge the battery. The 110v and 12v sides were separate. I could only use 110v with generator or shore power. And only 12v from battery. I recently changed it out for a newer Parallax converter to fix this problem. I also use a 15 watt solar collector (I mount to the roof) with a separate mini converter and 12v connection to the battery positive. I use solar source for remote camping (no shore power or generator) to charge my PUP battery during the day ... allowing me to use the heater (needs 12v fan to operate) as needed at night.

    KC
     
  6. Bill R

    Bill R New Member

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    Thanks for the replies. Interior lights while hooked up to the TV... that makes sense. I also agree there are to many splices in that line. I did not mention this originally but the line in question also changes gauges with each splice.
    So, to install a battery, I will run a new line from a new battery directly to the red line in the back of my converter. What is the suggested size wire for this. Is 10 heavy enough or is 8 required. And of course ground to the frame. Thanks
     
  7. Bill R

    Bill R New Member

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    KC,
    Thanks as well...real good information there
     
  8. rabird

    rabird Howdy!

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    10g would be fine, fuse @ battery 20A or up to 30A. clean frame (scrape off paint) for neg, use star washer and screw

    batt-1.jpg
     
    Sjm9911 likes this.
  9. GreyFox

    GreyFox Well-Known Member

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    No converter "powers" the trailer's 120 vac system, it merely serves as a convenient place to mount the 120 vac breakers since 120 vac has to be fed to the converter's input anyway. The converter's sole purpose when fed by 120 vac shore power is to convert that 120 vac to 12 vdc and supply it to the trailer's 12 vdc system, including charging the trailer battery (or batteries).
     
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