Headlight Switch

[Frostistamundo]

#61319146288 Headlight switch. What does the small (sensor) to the right of the switch do/control?

 

[Zedebee]

It’s the rheostat that controls the brightness of the dashboard illumination.

 

[Mr Tidy]

That's exactly what the thumbwheel does.

Or do you mean the little dot between it and the switch? If I had to guess I think it might be a light to tell you the lights are on and your Z4 may be an E89, as my E90 has that too.

 

[Rockhopper]

It’s some kind of daylight sensor I believe.

 

[Ben_Z4]

I'm interested in that too.
Also because in the day, my dashboard illumination was off and I wanted to switch it on, but couldn't find a way. Briefly thought it was broken, but then later when driving in the dark, luckily the dashboard illumination was on.
But does this sensor control the dashboard illumination? Or is the dashboard illumination switched on/off together with the headlights with the switch in Auto mode?