Hagar

I'm wondering if my auto dimming mirrors are actually working and how might one really tell?

I know my 04 UL needs the side rear view mirrors to be in "AUTO" to work and for the rear view mirror, you press the button and a green light comes on to tell you its working. But I watch these things and honestly, I can't see a difference or is it so subtle its hard to tell?

And what is that sensor in the middle of the dash just under the windshield?

LS430inDE.

Funny I've always wondered if my auto dimming mirrors work also. All I've done is push the button on the rear view mirror and toggle the green light on and off, but like you, I've not been able to notice a difference.

The sensor in the middle of the dash under the windshield is the ambient light sensor. In addition to possibly other things, it will turn on your headlights automatically if you have the headlights to the automatic mode, and also it will change the NAV display/brightness to night mode.

The ambient light sensor is quite responsive. Many times if simply going under an overpass, and the visible light diminishes, my NAV changes its brightness (dims) and I can see the indication on the dash that my headlights are now on. (I leave my headlight switch mode to AUTO about 99% of the time.)