Electrochomic Interior Mirror

The first time I accidentally bought a borderless mirror from VW Passat/Tiguan, but its arm is different and can’t be covered by a plastic cap from Audi. Many guys still install them by replacing both parts and caps. The shapes of the mirror for the A3 and Passat are also slightly different – VW is 2cm wider.

The original electrochromic borderless mirror of the Audi is installed on TT, Q2, and FL A3 models. Part number is 81A 857 511.

VW on the left, Audi on the right


I glued the large wiring diagram with a high beam assistant and a rain sensor, so it’s easier to get the whole picture:

For the full functionality, four wires are required (many guys do it with only two and lose some features).
By default, the Audi mirror has six pins:

1st – power
2nd – ground
3rd – rear running lights
4th and 5th – side mirrors control
6th – dome light

3th and 6th pins are used to disable electrochromic layer when you turn on the interior light or drive backward. For basic dome lights, the 6th pin goes to the pin 3 of the front ceiling lamp, for LEDs – to the 4th.

The 6-pin connector part number is 8K0 971 833. I bought a cable harness kit from Golf 7 on AliExpress and rewired it to support side mirrors. I brought these wires to the rubber band of the driver’s door and taped them here until the next round.

Stay tuned…

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