Rear View Mirror sensor?

Hi. I have a GTD with DSG....can anyone help with identifying what the small "sensor" on the back of the rear view mirror is for? I am considering a discreet dash cam which will obscure this sensor. See red circle on photo (not my car, just a similar mirror).

It's a light sensor, which detects the lights of the vehicles following you and dims the mirror for you

It's a light sensor, which detects the lights of the vehicles following you and dims the mirror for you

Fanis said:

It's a light sensor, which detects the lights of the vehicles following you and dims the mirror for you

Click to expand...

It is a light sensor , but it detects if it is daytime and hence will assit the auto dimming facilty of the mirror.

It is explained in the manual. That is the front sensor for the auto-dimming mirror. It helps to automatically dim the mirror depending on the lights of the oncoming traffic. It has a similar function to the sensor on the lower front of your mirror which reduces glare from vehicles behind you.

Avanti is right, I couldn't see the photo, so I guessed it was the one facing backwards!

Mine is in front and hasn't affected the light falling on the sensor.

Fanis said:

Avanti is right, I couldn't see the photo, so I guessed it was the one facing backwards!

Click to expand...

Fanis: your guess about a rear facing sensor is correct! But, OP's replies about the front facing sensor is also correct. If you think about it, the dimming effect must be informed by both the illumination of the road generally and the amount of glare from the headlights on the car behind you.

VW's anti dazzle mirror works by comparing the output between the forward looking sensor and the rear sensor. The greater the difference (the rear sensor is the reference), the more dimming occurs.

An easy way to see this effect is to completely cover the front sensor, and to shine a torch into the rear sensor (it's the small window next to the on/off switch facing the back)- with the ignition switch turned-on. What happens when you do this is that the mirror dims to maximum level.

On my car, I have placed a piece of non see-through tape over the front sensor, so that every time I switch-on the mirror I get maximum diming!

cheers
Don

Thanks you all. Your replies have answered my query.
Thanks for photo, Marnie, I didn't realise the roadhawk could be fitted so neatly in front of the mirror. I am trying to find a good dashcam that can be hidden by the mirror (hidden from my driver view that is).