All dash gauge and navigation lights go dark and unreadable when going from bright daylight conditions to shady conditions such as driving under a dark grey cloud shelf, in heavy rain, or even driving into tree shade. When you are in heavy downpour at 65, 70, or 75 mph it can be very panicky to not only drive but see your speed. Only very, very faint gauge info and nav info are displayed, so you cannot tell speed or if under guidance, where your turns or lane guidance info are. 2 Buick dealers have "flashed the chip" and occurances have lessened, but still there. One instance only "fixed" by restarting the car after taking a highway exit, the other I could restore by using the dash light brightness option after holding the switch for 15 seconds. The vehicle was in motion each time at varying speeds both in city and on highway. We shined a flashlight on the sensor located center front of dash with no return to normal intensity. I think problem lies in both the programming and the light sensor circuit itself. Service personnel cannot duplicate (of course). This 2nd report to you, the chip was flashed after that report. Thanks.

- Vail, AZ, USA

2 hours after sunrise or 2 hours before sunset, if driving on a sunny day and drive into tree shadows, both the instrument panel and the intellilink system displays go completely dark. This is with no external lights on (why should they be on a bright sunny morning or evening?). returning to sunlit stretches do not make the panels go bright again. You have to turn off the ignition and restart the car to bring the panels back to daylight intensity. You have to stare at the dark panels for 5 seconds to see if you can read anything, which you cannot, and this is making for eyes-off-the-road-time very dangerous. Made a service appointment 2/22, but only the salesman and service writer looked at car in the service lane and stated nothing wrong. The car did not enter the service bays at all, but only 1 service requested so far.this problem has happened 3 times; 2/22, 4/16, and 5/11/17. I saw on a Buick Envision trouble web page where 1 person with same problem said they found a service bulletin for this, but no reference to where they found it or the bulletin itself. I am still looking and am going to make another service appointment, but in person this time and not via the dealer's web page. This is a dangerous driving situation.

- Vail, AZ, USA