BMW i3 Dash Cam Mirror

A very specific project for mounting a very specific dash-cam mirror to the i3 mirror mount without strapping it on with rubber bands.

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The problem is simple. How do I see out of my rear view mirror with a 55lb Bernedoodle head planted right in the way? The solution, a 12" dash cam rear view mirror.

The mounting system of most of these types of mirrors is a basic setup with some hooks, and some rubber bands that hold the mirror against the factory mirror. This system is adequate, simple and provides a universal application to any vehicle. Most consumers are satisfied with this application, however the engineering consumer, will scoff at such a primitive design. The sight of wires in a vehicle causes this type of consumer a deep sadness. There must be a more complicated very specific part that is needed, right? Correct. This is that part.

The goals of this project are to design a reversible semi-permanent mounting solution that is:

  • Sturdy.
  • Functional.
  • Aesthetically pleasing.
  • Continues to allow the alarm LED (aka Clown Nose) to function.
  • Allows access to the SD card on the dash cam mirror.
  • Hides the wires required for the dash cam mirror to function.

The BMW i3, as well as most BMWs, uses a photochromaic auto-dimming mirror. This mirror has two sensors for determining how much to dim the mirror, as well as being connected to to a reverse signal wire, to override the mirror dimming feature providing full brightness while the car is in the reverse gear. All of this circuitry is attached to a small PCB and shoved in the mirror housing. This PCB also connects a small LED to the alarm system that blinks when the alarm is activated. The alarm LED is encased in a smoked plastic bubble known as the "Clown Nose" and it is the least favorite aspect of this factory design.

Dash-cams are gaining popularity with consumers around the world as they provide you with a continuous recording solution to capture all the shenanigans of your fellow road mates, catalog astrological events, spot UFOs, and hopefully generate viral footage for youtube. There are a number of dash-cams popping up that allow for a rear facing camera for ensuring inclusion of events that happen behind you. These systems can also be used to replace your glass mirror, with a much more sophisticated, error prone, less reliable, yet insanely cool digital rear view mirror.

I see no better combination than a digital rear view mirror and an electric car.  Follow along in the build logs for the specifics.

Mirror Mount.stl

WIP. The top wire cover cap needs to be redisigned as my first one has failed. This is fully functional as is, and is being used in my vehicle right now.

Standard Tesselated Geometry - 1.50 MB - 09/03/2020 at 19:33


  • 1 × 5mm Red LED
  • 1 × 1 kΩ Resistor
  • 2 × Breadboard Jumper Wires Dupont Male Ends
  • 1 × 12" Dash-Cam Mirror PORMIDO Mirror Dash Cam-Backup Camera 12"
  • 1 × Dash-Cam Mini USB Hard Wire Kit PORMIDO Hardwire Kit for Mirror Dash Cam PR996

View all 7 components

  • 1
    Alarm LED

    This circuit board that is included in the i3 mirror contains all the bits needed to make the OEM mirror dim. It also includes the LED (grey arrow) that will blink when locking the doors, and when the alarm is activated. I wanted to salvage the LED functionality, while ignoring anything else this circuit board wants to do.

    From what I can tell the wires are as follows:

    • Brown, Ground (-)
    • Red, 12v Constant ACC
    • White/Black Stripe, Reverse Signal Wire (did not test voltage)
    • Blue, 12v LED (+) load applies intermittently for blinking.

    Testing the board with a multi-meter revealed that the LED is simply attached to a 821Ω resister, and the ground plane. To reconstruct this circuit, I simply soldered an 1kΩ resister to the cathode and connected to the brown wire, then connected the anode to the blue. Wrap it all up in some nice heat-shrink, and use some breadboard dupont male jumper wires so that we can just plug it into the factory connector.

    When fully assembled, I added a bit of hot glue to stick the LED in the hole on the mount that fits the factory sensor light diffuser and snaps into the mount shell.

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