How to confirm the thing is selecting/changing when followed by high beams ?
Cannot discern if it is working. Tried a flashlight and noticed no change. How does it work ?

 

Sensors and Electrical Current through darkening gel. Have you tried it with actual headlights behind you?

 

Simple test


With ignition on:


Feel the backside (windscreen side) of the mirror housing for the little photocell indent, cover that to trick the mirror into thinking it's dark, then shine a light (daylight should work) on the mirror, it should darken over a few seconds to block the reflective mirror surface. Remove cover (finger?) from backside photocell, should go clear again (or turn off ignition).


Good mirror, GENTEX (NAS=GNTX).