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Thread: What's this third Wire "to back a car"?

  1. #1
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    What's this third Wire "to back a car"?

    I just bought a new 8.4" touchscreen on ebay, and I dont know how to wire it. The lcd itself has 2 cables that extend about 4 inches past the lcd. One is for vga, and the other is a combination power/AV input. It looks lika an s-video connector. Anyway, the lcd shipped with a cable to connect to the power/AV input. In addition to the audio and video inputs, it has 3 spliced power connection wires. One says "+12v", the second says "ground" and the third says "to back a car." How do I power this? Do I connect the +12v and ground to a car adapter (or psu molex)? What do I do with the "to back a car" wire? Please help. I do not want to fry my first LCD. See pictures for details.
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  2. #2
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    Quote Originally Posted by daveygravy View Post
    I just bought a new 8.4" touchscreen on ebay, and I dont know how to wire it. The lcd itself has 2 cables that extend about 4 inches past the lcd. One is for vga, and the other is a combination power/AV input. It looks lika an s-video connector. Anyway, the lcd shipped with a cable to connect to the power/AV input. In addition to the audio and video inputs, it has 3 spliced power connection wires. One says "+12v", the second says "ground" and the third says "to back a car." How do I power this? Do I connect the +12v and ground to a car adapter (or psu molex)? What do I do with the "to back a car" wire? Please help. I do not want to fry my first LCD. See pictures for details.
    Though there is really no way to say 100 percent what it is, it sounds like it is a 12 volt trigger to make the screen turn on the AV part of the input, for a reverse camera.

    Unless you have a reverse camera, you probably don't need to connect it.

    Try just the positive and negative wires, and see what happens.

    Michael
    ...I love the French language...especially to curse with...Nom de Dieu de putain de bordel de merde de saloperies de connards d'enculés de ta mère. You see, it's like wiping your *** with silk, I love it.

  3. #3
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    to be safe you would need to connect the +12 to the computer's psu. the rec. input voltage is 11.5-13 volts. the car's electrical system usually sees 14.4 votls while driving, so you'd fry the screen if you just hooked it up to the battery.

    the 'back to car' lead is probably a relay type lead that you hook up to your back up lights on your car. when the lead sees 12volts it'll most likely switch to the second rca input that would (usually) hooked up to a rear view camera. this way...when you put the car into reverse it'll switch to the rearview camera automatically.

    make sense?
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  4. #4
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    I would try it to ground first. If it doesn't ground then you could try 12v, but if it wants ground and you give it 12...no good.

  5. #5
    MySQL Error scott_fx's Avatar
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    very good suggestion. better safe then sorry. actually, before you even do that
    New System in progress:
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    Phaze TD1500 ~> Dynaudio MD130
    Phaze TD1500 ~> Seas g18rnx/p
    Zapco Ref 500.1 ~ 12" tc-9
    Behringer DCX2496 ~ Envision Electronics psu
    Transflective Xenarc

    My Car Pc Install
    My Boat Pc worklog

  6. #6
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    Guys, thanks for the advice. I ignored the third wire, and got it working. The manual had nothing useful at all, by the way.

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