The part that controls the brightness of panel items such as the radio, mileage use guages etc., is not working properly

Just purchased a pre-owned 2007 Silverado. When the **** that controls the brightness of panel items such as the radio, mileage use guages etc. is turned to dim (farthest counter clockwise), we have experienced these panel items becoming bright sometimes. This usually happens after a few minutes of driving or the next start up time. I is almost like a solar factor when vehicle is in the sun, it activates the brightness. Is this a normal occurrence? This **** can be pushed in or out for use. Does this make a difference? Hope this is not an electrical issue. All the truck functions seem to be working fine.