Electronic day/night mirrors have senors pointing toward the windshield and the rear of the vehicle. I happed to get an identical salvage, except different mount, mirror at the time the glass broke. The mirror also contains map which are used as interior lights. The original problem was not mirror related. Using the salvage mirror, the dome circuit would not work at all.
In any event, I learned that technology changed in 14 years from a liquid fluid to gel and the sealing is done differently. I also learned that at 14 years, the lifetime is about up. All of this info from the OEM.
So, it made more sense to repair at slightly over $100 USD.
In any event, I installed the new mirror when the salvage mirror was actively dimming and noticed that it dimmed too much. I held a pair of sunglasses over the sensor and the response was more to my liking. On another vehicle I cut a piece of sunglasses and glued it to the sensor to change the response. In this case, the new and old behaved differently/
A piece of Kapton tape was a simpler solution.
The adhesive is stable to 200+ C and removes very easily.