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Thread: 12v power source

  1. #1
    Join Date
    Aug 2017
    Location
    Blairsville GA
    Posts
    2
    My Cars
    2011 x3 35i

    12v power source

    Can anyone tell me where I can find a switched 12v source under the hood of a Z4 M40i? Very low amperage is needed.

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  2. #2
    Join Date
    Nov 2016
    Location
    Charlotte, NC
    Posts
    1,367
    My Cars
    '02 540i-6, '97 540i-6
    I can't speak to that car specifically, but you probably have several options.

    An easy one is the positive terminal of the battery or the "+" post that BMW puts under the hood (when the battery isn't there). If you do that, you'll still want the connection to go through a fuse. So use or add a fuse holder between the positive connection and the device you want to power.

    That connection wouldn't be switched on or off by anything in the car, so it would be always on.

    Another easy approach is through the fuse box. Often people remove a fuse to something little used, or less essential, put a wire in the negative side (opposite the positive side) then shove the fuse back in to hold the wire. That way the original circuit will stick work and you'd have power for your device.

    You can also use that approach to have it switched on by the ignition, or not, depending on the circuit you choose to tap into.
    Last edited by R Shaffner; 08-21-2021 at 12:14 PM.

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