Rear View Mirror

How does the little switch work that darkens the rear view mirror?

You actually have two reflecting surfaces in there. There is only one mirror but it is not cut from a flat piece of glass. In cross-section it is slightly wedge-shaped.

For daytime use you are seeing the full reflection from the silvered back. When you flip the switch the mirror’s position is altered. You then see the weaker reflection from the mirror’s front surface.

Or, were you talking about the electronic ones?

You can google “electrochromatic mirror” this might answer the question you are asking,Im not sure if its what you are asking. Never be afraid to tell make,model,year,and any thing else you think will help you get a quality answer.