On my 2010 Challenger the fan control knob on the dash can only be turned 3/4 of the way and then the fan cuts out. This happens with heat or AC. Has anyone experienced this? Is it the control knob, the resistor in the HVAC box or is it the fan? This has been going on for awhile.

Another issue that just came up is that it seems like the HVAC fan is now whistling when the AC is on. Is that the fan motor going bad?

Are they related?