Heater / AC motor stays on high...

[Willyone]

2016 Silverado Z71;  Problem is, when on "auto" mode the blower motor seems to stay on its highest setting, even after the cab temperature reaches the temp I set it at. I'm able to manually adjust/slow the motor down by just turning the fan speed down with the knob. I know, minor problem, I think (and hope). The fan speed would slow down automatically up until about a week ago. Question is, is there some setting, a procedure, easy cure for this glitch, or is there a sensor or something else that needs to be replaced?

 

Any help or input is appreciated!