12 volt power to trailer from truck???

Discussion in 'Trucks and Trailers' started by FIRESCOOBY, Dec 23, 2006.


    FIRESCOOBY LawnSite Senior Member
    Posts: 981

    Ok, I did search, but didn't find what I was looking for.

    I have a lawn care business on the side. I am planning on buying an enclosed trailer next year. For 99% of my accounts I must park in the road. Some of these are at the crest of a hill. I place cones out, but sometimes it isn't enough. I'm wanting to mount some small TIR3 LED amber lightheads on the rear of my trailer at the top. This we place the warning light high.

    Question: Is there anyway that 12 volt power can be fed to the trailer?

    I know nothing about trailers that require anything other than standard flat connector. This trailer will have trailer brakes and breakaway kit...if that matters.

    Thanks in advance.
  2. LindblomRJ

    LindblomRJ LawnSite Silver Member
    Posts: 2,570

    Yes, on a pin trailer tow vehicle plug setup on of the wires is constant hot (connects to battery)

    e-trailer dot com has wiring diagrams. I think it is the center pin on a 7 pin setup but don't quote me.
  3. mad_wrestler

    mad_wrestler LawnSite Senior Member
    Posts: 339

    that's right RJ
  4. FearThisDeere

    FearThisDeere LawnSite Bronze Member
    Posts: 1,168

    Yup, everyone is right. How are you going to power the strobes though? Do the TIR3s require a special strobe power box? I am not too familiar with strobes. I know that you do have constant power from the truck to the trailer on a 7 round plug for something like backup lights, but I don't know about strobes.

    FIRESCOOBY LawnSite Senior Member
    Posts: 981

    They're not strobes. They are self contained LED modules. Very bright for their size and have built in flash patterns. All I would need is power to the lights.
  6. John Gamba

    John Gamba LawnSite Fanatic
    from ct
    Posts: 10,812

    use connectors like they use on jumper cables, there just smaller. I can post a pic of what i'm talking about tomorrow morning if you need it.
  7. muddstopper

    muddstopper LawnSite Silver Member
    Posts: 2,342

    The center pin on a 7 prong flat rv plug is not the power supply, it is for backup lights. The accessory wire will be on the top right hand side of the recepticle. This pin should be 12V positive at all times, even when the trailer is unplugged. This is assuming that the recepticle is mounted with the flap opening upwards and not in some other direction, and with you looking into the recepticle at the pins and not at the back of recepticle where the wires are connected. The wireing sequence should be as follows in a clockwise direction. Top right acc.-red or black wire. Middle right, right turn- green wire. Bottom right, trailer brake-blue wire. Bottom left ground-white wire. Middle left, left turn-yellow wire. Top left, tailights-brown wire. Center pin is backup lights, not sure of color but most trailers dont have backup lights. This is standard wireing for most ford chevys and dodges, but not all trucks are wired in this manner so always check before hooking up. Also, the color codes listed on most of the 7prong rv plugs I have bought, where it is stamped in the back of the plug, doesnt match this pattern, so if you just try to match wires to the color codes your lights probably wont work. If you buy a new plug, it will give this wireing pattern, but also gives you the same warning to check your wireing before connecting.
  8. muddstopper

    muddstopper LawnSite Silver Member
    Posts: 2,342

    I tried to edit , but was to late, The new trailer you buy should have the breakaway kit already on it. This will include a 12v battery for operating the trailer brakes "if" the trailer was to get lose from the truck. The accessory wire in your plug should be wired so that it can keep that battery constantly charged. Simplest hookup for your strobe lights would be to run a fused hot wire from your breakaway battery to a switch and then to the lights.
  9. Eclipse

    Eclipse LawnSite Bronze Member
    Posts: 1,149

    Most enclosed trailers have lights inside. Just grab power off the interior lights. This way they are on a switch already too.

    I don't know that I would mount them at the top as the TiR3's are not the greatest off axis. I personally would put them 1/2-2/3 from the way up from the bottom.

    BTW - I just bought a set of Amber Tir3's to do this exact same thing :)
  10. Albemarle Lawn

    Albemarle Lawn LawnSite Bronze Member
    Posts: 1,544

    Your breakaway battery should be plenty. The breakaway batteries are typically 4 AH rated lead-acid batteries.

    In leiu of connection to 12V vehicle, I have placed a small VW solar panel on top of the trailer.

    Go to EBAY and enter VW SOLAR as a keyword.

    Volkswagen uses solar panels to keep the batteries fresh on cars in transport. They wind up on EBAY after dealers give them away. They are very good panels and put out up to 0.3 amps.

    For permanent install, you could build a waterproof lexan (plexiglass) box and permanent mount on the roof.

    The big advantage, your breakaway battery is always fresh.

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