Problem with my new 2019 Charger - automatic dimming mirror would NOT EVER dim under normal night driving conditions, however, it did work under test conditions - 'drove' me nuts. (Test conditions = turn vehicle ON to ACC, make sure Auto Dim was ON at the UCONNECT display, fully cover the mirror's front light sensor and shine a flashlight into the rear view mirror sensor (at the top of the mirror). Under test conditions it automatically dimmed great and fast (less than 5 seconds). So...no electrical issues in my situation.

The only residual cause for the mirror to not automatically dim was either the front and/or rear mirror sensors are blocked from stimulus (light rays) during operations. So I took a look at my mirror sensor alignment (TOP of mirror) and the expected light path back to a following car...I found that this path was MECHANICALLY BLOCKED by my car's ceiling console, which was not fully/flushly installed up into my car's headliner! (The ceiling console is the control head for sunroof, lights, garage door, sunglasses holder, etc.) For my Charger the Dodge factory builders only engaged 2 of the 4 console mounting clips, leaving the console edge closest to the mirror HANGING too low, which blocked light vectored from the rear from entering the top mirror sensor. Following the Dodge technical data (from techauthority.com) I was able to locate the correct pressure points for the other 2 clips and properly installed the ceiling console. Just this 1/2" clearance gain makes all the difference for sensor light ray detection...my auto dimming mirrors perform as expected now. Case Closed, but what a pain.

Note: as long as I was looking into the center console situation I noticed two other shoddy workmanship areas with respect to the inside lining - mismatched ceiling liner junctions and front pillar liner separation. Recommend you take a look at all interior trim too. Good luck.