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Activating Tesla's Photochromic Rear View Mirror ?

Discussion in 'Technical' started by 3mp_kwh, Dec 15, 2016.

  1. 3mp_kwh

    3mp_kwh Member

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    Boston
    #1 3mp_kwh, Dec 15, 2016
    Last edited: Dec 15, 2016
    I suspect this post will sit, dead, but have gotten further than perhaps others stuck without a night mirror in their Model S. In post-AP Tesla's, the night mirror is not always active as I believe "photochromic" was a positive option of the tech package. It's a lame situation, as there is no manual flip for headlights from behind and Tesla refuses to fix it, or even be paid to fix it. They claim the mirror is part of the AP system, but it's made by Volvo. So, I'm going public with where I am, with a white flag for those who might have the access to know better. So far,

    -Inactive photochromic (night) mirrors become functional, if put in cars having the tech package. So, this isn't hardware.
    -A vertical 5-wire DIN plug feeds both.
    -Top two wires are steady 12v, for both functional and non-functional cars
    -middle wire is dead, or shows 1.3V with mirror activated by a light source in the car having the "photochromic" option
    -bottom two wires are dead, and open circuit (full resistance) with no light
    -with light, the two bottom wires form a circuit (zero ohms), if attached to the mirror when it receives light. You begin to see resistance return as the light goes away (light sensor is on the mirror glass side).

    I believe a closed circuit could be telling the car's controllers to send 1.3V to the middle wire, but haven't got the Tesla back end tools to know. So, the question for anyone with them (WK057, Ingineer...) is whether that is the case, and if the feedback coming from the mirror's closed circuit can lead to 1.3V, instead of 0V, coming back from the car?

    There's another way to do this, by perhaps coming up with a 1.3V source, but that would be a mechanical hack (maybe a AA battery). I'm leaving this riddle to seek a bit of help, and maybe help anyone else perplexed by how their ~100k car ended up without even a flip mirror... Almost there... Thx.
     
  2. ⚡️ELECTROMAN⚡️

    ⚡️ELECTROMAN⚡️ Fritterer and waster of hours in an off hand wayer

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    Portland, Oregon
    You were right. This thread never got off the ground. Ironically I found it by searching for a way to turn off the photochromic feature. After tinting my windows the mirrors are now too dark. Do you have any idea how to turn this feature off?
     
  3. obrien28

    obrien28 Midnight Engineer

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    NW CT
    Just came across this, I think there might be a way to enable the mirror, it looks like it is controlled by the cars LIN bus, like CAN but designed for less critical devices. Might be possible to spoof the command it needs. PM me with an email if you are interested.
     
  4. 3mp_kwh

    3mp_kwh Member

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    Usual safety disclaimer: No idea what else this could do.

    First, the easiest to try would be taping over the light sensor on the reflecting side. The mirror looks only like a mirror, but if you shine a flashlight you'll see through where the ~1cm sensor area exists.

    With disclaimer made, you have one trim piece to remove, to gain access to the 5-wire DIN going into the back of your mirror. I have the manual for this step. If you trace around where the mirror meets the glass, you'll notice about a half moon radius of plastic. Flare both ends of that out with a trim tool, and pull straight down. It should unclip. Then, you should find, on at least the AP and later cars, that the plug is held in by a tab facing the passenger side. Push it in and pull out the plug. At this point, the five wires, stacked vertically, when the car is in 'Drive' provide (photochromic is bypassed if the car isn't in 'Drive'):
    1 - 12v
    2 - 12v
    3 - 0V with no rearward light source, 1.3V with a light source
    4 - 0V, full resistance without light, zero with
    5 - 0V, full resistance without light, zero with

    So, 4+5 complete a circuit when light shines on the reflecting side of the mirror. The rest is up to you. I have never driven with one disconnected. Safer to try may be a bypass of #3. If you simply put a small piece of tape on the front, the open circuit should prevent the 1.3V from dimming things up.

    PS - Thanks, obrien28. You have PM.
     

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