I have a 2013 GL450 (x166). The HVAC fan keeps randomly going from low to high, then back to high. If I select something with the controls, it will change on the screen, but the lights on the button won’t light up. For instance, in the past - auto, off, etc, would illuminate the red light on the button. I’ve tried turning it off and manually controlling the fan speed, and neither works.

Any ideas on where to start my troubleshooting? Also, can I pull a fuse or something to turn off the system, until I have time to look at it?