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Electronics amateur here.

I bought a dash cam, front and rear. The rear cam currently feeds into the front cam, and records just fine. The front cam is powered by the cigarette lighter.

However, the manual tells me that if I give the rear cam power, it's supposed to show me fancy parking lines when I reverse. To do this, I'm apparently supposed to connect the back up cam's "red wire" (there's a dangling red wire on the rear cam that goes nowhere at the moment) to my car's reverse light. For various reasons, I can't do this. So I want to connect it to my car's cigarette lighter.

I bought a cigarette lighter splitter, so I have extra sockets there.

I bought a cigarette lighter "inverter" (max 15amps) which basically plugs into the cigarette lighter, then has a 10ft red wire (positive) and black wire (negative) which both end in a "lug" connection. I also bought a switch.

So, I figure I should just run the inverter's red wire through the switch, then connect it to the camera's red wire and voila? (right? wrong?)

But what do I do with the black wire? Is there a risk in just covering it up with electrical tape and letting it sit there eternally?

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    You'll need to give more information than this. – Hearth Jul 4 '19 at 19:46
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    So basically, you want to connect it such that your camera always has parking lines? I would assume you could just connect both the red and black wire to the cigarette lighter. I don't know why you bought an inverter though. That has nothing to do with anything. – DKNguyen Jul 4 '19 at 19:46
  • Cigarette lighters aren't always on though are they? There could be issues if the car's primary electrical power isn't being fed to the camera but the cigarette lighter is feeding power into the reverse light inputs. – DKNguyen Jul 4 '19 at 19:52
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    The term "inverter" usually refers to a thing that takes 12V in and puts out 120V or 230V AC. I do hope you're not planning on sticking 120V into the input of your camera. – Simon B Jul 4 '19 at 21:45
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    Please provide some more info on the product. A link is ok, a diagram and part number are much better. – Drew Jul 5 '19 at 1:47
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The red wire alone should suffice. The black wire should not need to be grounded, as the camera system should already be grounded through it's primary power connection to the lighter socket. I'm not sure what your mean by inverter, as that is a device that converts DC to AC, and has no place in solving your issue. I would assume that instead you mean an "extension"...

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  • Amazon calls it an "inverter" even though it looks like a simple extension. But I cancelled that order and will get me something else that is definitely only an extension in case this thing is indeed "inverting." Thanks for the answer. – Paulo Jul 5 '19 at 16:47
  • I don't really understand your logic of why you wouldn't need to connect a ground cable to ground. – Christopher Hunter Jul 5 '19 at 18:39
  • @ChristopherHunter-The scenario he is describing includes a lighter socket splitter, with one of the outlets providing power and ground to the camera system, and the other outlet providing the 12 volt switching signal to camera overlay enable through an extension wire. Since the camera is already grounded, there is no need to run the black ground wire from the extension to another ground point. The black wire is already at ground potential. – Hitek Jul 5 '19 at 19:02
  • @ChristopherHunter-Also keep in mind that I am an engineer that provided this answer before this question was migrated from electronics.stackexchange.com, where common ground is an underlying base principle. I'm not sure if you understood that the "hanging" ground wire he was referring to was not a source of ground for the load(the camera system), but rather an extra ground from the power source, from which the ground of the camera system is already connected. If it was you that downvoted my answer due to a misunderstanding, I would ask you to reconsider. Thanks. – Hitek Jul 5 '19 at 19:42
  • @Hitek I think without a pic or diagram it's really impossible to say exactly what the situation here is. I do understand common ground and have done a number of successful electrical mods to vehicles, including setting up a backup cam very similar to this. Whether you are an engineer or not, your answer assumes several things that I just feel aren't clear from the question, including whether the black wire from the switching circuit actually is connected to ground already. I would be very suspicious of why the wire is there at all if it's already been grounded internally. – Christopher Hunter Jul 19 '19 at 17:58
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It's hard to give a clear answer without knowing the exact wiring layout, so providing a diagram or photo would help a lot here.

That said, the dangling red wire is intended to connect to the backup light and will either provide power for the device directly, or will switch it "on", and the power is connected via another set of wires. You mentioned having a switch, so you probably want to connect that red wire to one side of the switch and any power source to the other side, such as from your cigarette lighter. This would allow you to toggle the reverse cam on and off (which is what I assume you want to be able to do).

I would assume the black wire should definitely be connected to a ground point somewhere. There normally wouldn't need to be more than one, but you need something to complete the circuit.

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