12V Power in the Trunk?
 

I have an external GPS unit I want to mount in the rear window. Since it requires charging, I need to tap into a 12V line somewhere that has constant power when the car is powered. Does anyone know whether the closest source for power the cigarette adaptor in the central console, or is there somewhere closer I can tap into? I do have the OEM Audio+ subwoofer, so I assume there is power going there, but I'm not sure which wire is the power wire, nor the voltage.

Thanks.

glove box? Are you using that one?




Edit - nevermind - I think you're looking for a +12V line....but, the glovebox might still be the answer!

I'd like to mount it in the rear window, so I'd prefer something closer, only because tearing apart the car to run the wires is such a PITA. But thats a better location than the center console, actually.

The amp in the trunk should have a 12v lead you could splice into.

Thanks - that's what I was hoping...

FOr anyone else looking to do this - this worked but produced a pretty serious buzz, I'll just run a USB cable to the glove box. Thanks.

Does this GPS wire directly into 12v vehicle power, or does it run on 5v USB power? If it runs on USB, and you run a USB cable to the glove box, I'm assuming you plan to use a USB adapter in the glove box cigarette plug, in which case it will not be available for anything else.

Although there's nothing wrong with that, I personally wouldn't do it that way, for a few reasons. First, USB cables are way overpriced, and a USB cable that length is not going to be very cheap. Second, you can almost never find a USB cable that is exactly the length you need, and it's difficult to cut them to custom lengths without ending up with something pretty ghetto. Third, if it's intended as a permanent or semi-permanent installation, I would rather not have it always taking up an accessory plug that I might need for something else. Finally, I'm not sure what the clearances are under the trim, but USB cables are rather thick and not very flexible.

Instead, I would get some 18 gauge automotive wire (cheap and readily available at Home Depot, WalMart and any auto parts store) and run it from the trunk to the fuse box under the driver's side dash. Tap into the fuse box using an add-a-circuit, also available at auto parts stores (or available in 5 packs for really cheap on eBay). The wire run is going to be almost exactly the same as the run to the glove box, just on the opposite side of the car, but with much thinner, more flexible wire that will be easier to work with and conceal. Find a ground point in the trunk area.

Then you'll have an extra 12v power circuit in the trunk. If the GPS can be direct-wired, wire it in and done!

If it needs 5v USB power, just add a USB adapter. You can buy them for direct mount (like the one in your dash) and mount it wherever you want, but when I wanted one under my dash for USB power to run a tablet, I just cut open an inexpensive USB cigarette plug adapter and mounted it with foam tape. You can usually pick up cigarette plug adapters at close-out stores like Big Lots for around $5 each. I prefer to get the 2.1 amp adapters for the extra power.

I soldered and heat-shrinked mine, but all this can be done with crimped connectors (also available cheap at Home Depot). If you go with a cheap adapter that you cut open, be careful of the leads to the circuit board, because they are usually very thin and not very securely soldered. When I did mine, I desoldered them and soldered the 18 gauge wire directly to the board to avoid having a ghetto connection.

It's slightly more effort to do it this way, but you'll end up with a custom solution that provides just the right amount of wire to the mounting location of your choosing. I was in a rush when I tapped into my fuse box, so I just piggybacked on the circuit for the seat heaters (which I never use) so that power would be killed when the car is off. I believe some of the unused circuits in the fuse box would provide the same power, but I've been lazy and haven't bothered to test them.

An 8 ft USB cord + a 12V splitter was under $20, and I already have a two port USB/12V adapter. If I don't like it, I may look into direct wiring, but at that price, trying this first was a no brainer. The glovebox outlet shares power with my Passport Escort Max, and I can have a phone charger and the GPS in the dual port. I don't need more than that on a regular basis, and in a pinch I can use the USB radio port or center console for USB power.

I hadn't heard of the add-a-circuit but that does look interesting if the above doesn't work.

Why is the gps going on the rear window?

Better line of sight and certain track organization don't allow non-oem fixtures in cars. So wedging it in the back is safer than the front.