Touareg: 2008 R5 TDI
Join Date: Dec 2016
Second Vehicle: Still looking
Thanked 35 Times in 33 Posts
The easiest way would be to just cover the light sensor with some opaque material, like a piece of tape, so the mirror never realizes it's being sheen at. Or if you want to make things complicated, you could disconnect the electronics part of it, or adjust its sensitivity (ie. the point at which it starts to dim) in VCDS.
However, if your problem is that it's also "dimmed" in bright sunlight, then that's because the layers inside the mirror glass have separated and oxidized, and you'll have to replace the mirror to fix that.