dimming rear view mirror

[marinabrid]

Evening all
Is there a way to test the interior mirror ,   its supposed to dim according to the book, but i cant see it seems to change,.   should it go very dark at night ?    i see a little sensor on the front and back so presume these have something to do with the way it works

thanks

[insanitybeard]

If I'm correct, the front (forwardmost) sensor detects ambient light and the rear one detects light from headlamps shone from behind when driving in the dark. If my reasoning is correct, the way to test would be to cover the front sensor with some opaque tape (to fool the sensor into thinking it's dark) and then shining a light source into the rear sensor, you should then be able to see the mirror dim if it's working properly.

[marinabrid]

Thanks for that    will test it

[Mirez]

All my previous VW's have had a switch on the bottom of the mirror, I can't say I've ever looked at the Galaxy but it may also have one.

It's also only powered when the headlights are on and also won't function if the car is in reverse

[SilverBeast]

...also it doesn't dim very quickly.  I thought mine wasn't working for a couple of years before finally figuring it out!

[marinabrid]

managed to check it while daylight as suggested.,   blocked the front sensor and shone light into other, you do need to stare a fair while  but you can then see the glass darken,  then lighten up much faster when sensor uncovered
thanks for all help