Well that's not good news. I'll have to keep an eye on it. As far as adjustment, the sensor is a single piece of molded plastic. There is nothing to adjust there on on the harness that I saw physically or on the schematics.

A simple solution would be to get something that is tinted and put it over the sensor. Even a small translucent plastic cap might do it and if you find the right size it would look pretty factory. Less light would hit the sensor and sensor would read darker than it really is. I'd start in the dollar store and see if there is a kids toy that might have a part you could re-purpose.

I almost played with the sensor with my meter to see how it worked (probably uses resistance but which way - 0 resistance could be day or night) but since it was $100 I decided it was better left alone.