I bought my car new in December 2016. My auto dimming mirrors don't appear to be working. (I'm not a fan of auto dimming mirrors because they never get dark enough for me on any car I've driven). In an effort to test the system I covered, with my hands, what I believe to be the sensor on the left/back side of the rear view mirror as well as the sensor on the left/reflective side of the mirror and nothing happens, no dimming. I'm doing this in bright sunshine. I've covered the back side only, the mirror side only and both at the same time. Does this indicate the auto dimming feature is not working or am I not testing it properly? The car is on and in drive during my testing. Not driving while testing. <grin>
I think mine "works," but I've complained rather bitterly on the forums about how badly it works. I think it would have been unacceptable on a 1970 Dodge. I've also written to Evannex suggesting that if they could offer an auto-dimming or, even better, a manually dimmed replacement rear-view mirror, they'd sell a lot of them. They replied that they've had several inquires just like mine, enough that they're looking into producing a replacement. The problem in developing an aftermarket replacement is that the sensor in the interior rear-view also controls the dimming function of the exterior mirrors.
What you didn't mention is the frame around the mirror. Even if the mirror dimmed normally, I'd be tempted to attack it with a hammer because of the mirror-bright metal frame that some retarded engineer or design stooge placed around it. That frame can be nearly blinding all by itself.
Tesla should be sorely ashamed of this mirror, the design of which was universally perfected within the industry way back in the last century. A few design goofs are inevitable in any new, complex product, but this one is inexcusably glaring (sorry, pun unavoidable).
BTW, I've found that yellow "night-driving" glasses are inexpensive and
do help with the shortcomings of the rear-view.