Adding auto dimming mirror to base model Prius

Discussion in 'Gen 2 Prius Audio and Electronics' started by John Hry, May 13, 2022 at 6:39 PM.

  1. John Hry

    John Hry Junior Member

    Joined:
    Mar 24, 2021
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    Location:
    Michigan
    Vehicle:
    2008 Prius
    Model:
    ----USA----
    I was at the junkyard and saw an auto dimming mirror so I decided to try and wire it up to my 2nd Gen Prius. There is no connector since it didn't come with it originally, so i tried wiring the mirror's 3 wires to the wires connected to the dome light in front of the center console. After it was wired up, I went to test it and only the Homelink was working and the auto dimming (green) light was not functioning. I tried looking back at other forums to see where people have wired it to in the past, but had no luck. If anyone knows what is wrong or has any ideas it'd be greatly appreciated.
    Wires.png
    ^How I did my wiring Homelink working.png
    ^Homelink working Auto dimming not working.png
    ^I get nothing out of the auto dimming
     
  2. John Hry

    John Hry Junior Member

    Joined:
    Mar 24, 2021
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    Location:
    Michigan
    Vehicle:
    2008 Prius
    Model:
    ----USA----
    I think I know what is wrong now. The way I wired it I sort-of winged it.. so it didn't work. When I looked up on youtube to find how the circuit actually worked, i realized the one wire i misplaced was the Ignition 12V (black wire in initial posting). So the Homelink was getting power and working as it should, but the auto dimming was getting no power. If anyone were to do this in the future you could wire the Red (Const. 12V) and the White (ground) to the dome light as I initially did, but for the black wire you would not want that to be on all the time, so you could wire it to something like the 12V power outlet where it would turn off as the car would. Diagram.png IMG_4361.jpg
    ^^^^^^
    Red (Const 12V)
    White (Ground)
    Black (Ignition 12V)
     
  3. rjparker

    rjparker Senior Member

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    Location:
    Texas Hill Country
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    The homelink garage/gate buttons always work even with the vehicle off. These buttons are run by the constant 12v as wired from the factory. In fact they can be a security risk if someone leaves an unlocked car outside of their garage since anyone pushing the homelink button will open the garage door. The off state current draw is 6 ma.

    The dimmer function is run from the switched 12v and has an on and an off button on the mirror. In a retrofit you can power the mirror's switched 12v from constant 12v. Even when run by constant 12v, the dimmer won't draw any additional off state power based on my measurements.

    Some might prefer to run everything from the switched 12v to avoid the above security issue.
     
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