hardwiring 12v (car lighter) GPS Unit? How?

Hi, I have a Garmin Nuvi GPS unit which plugs into my car cigarette lighter. On the one end it is a 12v cigarette adapter and on the other
end it is a mini-usb. It looks kind of ugly with all the wires hanging out. My idea was to purchase an extra 12v cigarette wire/charger for it and hardwire it to my car and run the wires behind the dash, but I don't know how to hook it up.
Can I just splice the wire into the 12v ignition power wire that runs to my stereo? Should I splice it in to the back of the lighter??? Will it have a positive and a negative? How can I hardwire it so that it will have current when the car is on (key is turned). I just installed a new receiver, so I am kind of in the zone right now as far as where all the wires are, so if anyone could provide some info on how to do it, then that would be great.
Just to reiterate, I want to buy a 12v car lighter to mini usb to power my Garmine GPS, cut the cigarette end off and hardwire it to the ignition so that it is powered when the car is on... How could I do this and how would be wired??
Thanks!@! -Rob
hardwiring 12v (car lighter) GPS Unit? How?
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I would choose the back of the lighter, or possibly the radio's switched supply. Check if your lighter is switched on/off with the ignition. Decide from there. Yes, there will be a 12V positive and ground. Look carefully at the wires on your charger before cutting the end off. There should be some way to distinquish between the two. Plug the cut off end into the lighter and measure to see which wire is 12V positive and which is ground. Be careful to hook up the other part in accordance with what you observe. Good luck, and be careful about polarity . . .
Bill Ranck Blacksburg, Va.
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bertbarndoor wrote:

I can check if you want - but I suspect that the Nuvi "lighter plug" contains electronics to reduce the nominal 12v of the car electrics down to 5 volt for the GPS. Chopping off the plug and hard-wiring it in with put 12v, rather than 5 v, into the Nuvi and release a lot of "magic, one-time, flame and smoke".
A safer way is to get a lighter extension cord. Plug the Nuvi power cord into it and hide most of both behind the dash - just leaving the two plugs( the Nuvi mini USB and the extension lighter plug) to come out near the relevant socket. I would suggest firmly taping the Nuvi lighter plug into the extension socket, to stop any possibility of it vibrating loose.
If you really want to hard wire it in - chop the *lighter* plug off the *extension* cable and hard wire the extension cable in. To be safe, you need to add an inline fuse. You can get these from Maplin. A three amp fuse should be fine. However, you do need to identify which core of the lead is which and do need to choose the right point in the wiring harness to connect to. I've seen a few car wiring loom fires in the past -so I would stick with an extension cord and a plug that goes into your existing lighter socket, IIWY.
-- Sue
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It does, the charging jack on the Nuvi is a USB plug, the lighter plug contains a 5V regulator so you can't just chop the plug off, but you could open it up and hard wire the regulator circuit board, or just buy a lighter socket and mount it in a concealed place with the charger plugged into it.
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Here's what I'm going to do. Thanks for all the suggestions all. I bought a female 12v cigarette lighter end from radio shack (aka The Source) and a few vampire taps. I'm going to go into the back of the dash find the hookups to the lighter and just tap in with the vampires. Then I'm going to run the GPS cord in behind everything and just plug the thing in to the new outlet. The lighter does come on via the ignition, so it isn't going to be constant juice which is good. I like the idea of taping it in so it doesn't vibrate loose. I think this is the best solution. The only issue I have now is trying to figure out the best exit point for the usb end that plugs into the Garmin. My prelude doesn't have anything obvious... I might *gasp* drill a hole. We'll see. Thanks again all....
ha ha, magic, smoke... :)
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bertbarndoor wrote:

If the "vampire tap" you mean what I would call a Scotchblock" connector:
http://www.elise-shop.com/images/ScotchBL.jpg
Do make sure that it is the right size for the wires used. (The wires going to the free socket should be the same size as the wires that you are taping into.)
Too small and there is a risk that the original conductor will be damaged. Too big and there is a risk of a high resistance connection.
I would repeat my suggestion (also echoed by others) that you add an inline fuse.
-- Sue
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The radio shack female cigarette connector has an inline fuse already attached to it. Saves me some trouble... Anyhow, thanks again for all the advice...
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