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Thread: Adding a 12V outlet to my car (image heavy!)

  1. #1

    Adding a 12V outlet to my car (image heavy!)

    I decided that I wanted extra 12V outlets, at least one more to start, after taking 2 ~1000mi road trips with 3 friends in my car. We made do with a 12V > 120V converter which also had a USB port and pass-thru 12V outlet. With this, I realized that wires around the shift knob and all that was quite annoying.

    After lots of research and reading many threads where others have added outlets, I deceided that I wanted to move forward with this and could pull it off. I had added an AUX input and mounted it in the tray in front of the coin holder, so I figured why not tie in a 12V outlet somewhere.

    Considering where there were 12V lines, and whether or not I wanted it to be switched or not, I had some choices to make. I opted for a switched outlet (no worries about draining the battery) and one that was pretty easy to access both for installation and use, but also out of immediate sight in case I botched my first job. Since BMW lets you plug a 12V converter into the flash light port, I decided I'd tie into the harness somewhere in the passenger footwell.

    Commence DIY! Total time required: 2-3 hours Total cost (if you have the tools): ~$20-30

    I went out and picked up some pieces I'd need. I didn't have many tools to start, so my shopping list is probably longer than most others would need.

    Harbor Freight dremmel

    HF super cheap multimeter (to say yes or no to continuity, 12V+, and GND)

    12V sockets from a Y-adapter (this yielded me 2 sockets and 1 plug for a side project)

    Some heat shrink

    14ga butt connectors

    14ga wire (the car's harness is smaller, but this is for my peace of mind, it could be smaller)

    in-line fuse holder

    5A fuses, I used 10A, but would feel better about 5A Also, automotive blade fuse holders are available and let you use any spares you may have for your car, but I didn't want to use the fusebox spares and had a 10A lying around.

    Electric tape

    Phillips head screw driver (PH 0,1, and 2, maybe?)

    Small screws (I used 2-56 x 3/8 machine screws because I could get them from work, but something the same size but more coarse would've been better.)

    Drill bit to drill pilot holes for the screws, sized appropriately, 1/16" in my case

    Super glue

    Heat source for the shrink tube (lighter, heat gun, hair dryer, etc.)

    After following guides for other guides for removing the glovebox, I removed the panel below the glovebox which has the ducting for the footwell air and light. I chose the nice flat patch behind the light as where I'd put the outlet since it was hidden, near where the flash light wires run, and not impossible to get to.

    Glovebox and plastic piece out

    Tools and hardware

    Testing the flashlight connector

    Now with the key to ACC

    My custom bracket (painted) to mount the socket, but it could be done with some 2 part epoxy/JB quick/etc., unless you also have access to a 3D printer (perks of my job!)
    x3g file for Makerbot Replicator 2
    STL file for your own post processor

    I butted the mount against the light housing and traced its inner diameter on to the backside of the plastic, grabbed my dremmel, and then cut the hole, using a sanding drum to make it fit snugly.

    I then flipped the socket around backwards to hold the mount and transfer the two bolt holes through the plastic.

    I slipped with the sanding barrel and knicked the plastic. It'll never be seen, but it drives me nuts.

    Attach the mount with the two screws

    Using one splice I had around, I attached the in-line fuse to the + end of the socket. This is the contact at the bottom-center of the socket. Using the multimeter, I tested for continuity and found it to be this wire.

    Apply heat shrink (I had to keep the bugs away from my work light somehow, and didn't have the lighter anymore)

    Not pictured is where I extended the wires a bit from the socket and in-line fuse and also added quick connectors. I put one on the ground at the same point where I spliced in the fuse and the second at the other end of the fuse. This way, they're stagged, will not short together (I still wrapped them in tape), and if ever disconnected, it's easy to tell which connectors go together since both wires should end up being an equal length.

    Now the scary part... Locate the wires running to the connector for the flashlight (The black cloth tape BMW uses is nasty stuff). Brown is universally ground, red is typically hot. Just double check with the multimeter. Black to brown, red to red. Positive voltage = brown/GND red/+

    I don't have pictures of the intermediates, but here's the ground of the socket spliced into the flashlight's ground. I cut the brown wire (don't cut red yet!), stripped it a bit, twisted the connector end to my new GND wire, and put it into one end of a butt connector. I crimped it and heat shrunk it. Next, I put the harness ground into the connector, crimped, and applied heat. This didn't shrink enough to fully seal, so while it was still hot, I pinched it a bit to close down on the harness.

    Before you get anywhere, test for continuity!!! If the wall of the socket and the ground of the connector have continuity, you're on the right track. Also test the wall of the connector to some exposed metal. The seat rails should work. If this has continuity, the splice is good.

    Repeat with the positive now. I didn't want to cut the positive until the negative was fully insulated again.

    Here it is in place, but before I even replaced the panel, I put the key in and tested the outlet as it sat there. I popped in a 12V > USB adapter and it lit up! Success!

    The final image, with the panel and glove box back in place. Dang, that glove box is a bear to replace. I recommend not doing it at 11pm like I did when it's tough to both wrestle it into place and juggle a work light.

    Also, an odd little bit I noticed while determining if/when/how this outlet would be switched. When the car is locked, it cuts power immediately and the outlet and flashlight are no longer powered. If you lock the car with someone seated in either of the front seats (I didn't test the rear), the interior lights fade slower and the outlet/flashlight stay powered, though I didn't test for how long. As long as you don't have something heavy enough to resemble a person in the passenger seat, this outlet will be powered off immediately when the doors are locked and shouldn't drain your battery.
    Last edited by nmac9; 07-26-2014 at 12:01 AM.

  2. #2
    Join Date
    Jan 1970
    Southern California
    Nice! Thx for posting the info.
    Randeaux/Rando/John/jr - '06 Cic ZHP; Southern California
    "ZHP or not, I still like you"

    ZHP Performance Package, Cold Weather Package, Leather, Jet Black/Black/BlackCube, NAV
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    Note: Actual car no longer resembles signature picture

  3. #3
    Join Date
    Jan 1970
    That's awesome. I been wanting to do the same for my jeep. So when I go camping.

  4. #4
    Join Date
    Jun 2011

  5. #5
    Join Date
    Feb 2011
    Valparaiso, IN
    Good job!

    Sent from my iPhone

  6. #6
    Join Date
    Jan 1970
    Lebanon, OH
    Quote Originally Posted by ryankokesh View Post
    Good job!

    Sent from my iPhone

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