Re: High pitched whistle sound from heating blower fan
I had a similar noise just the other day; a high-pitched whistle when the blower was on high. After nearly pulling my hair out, I tried raising all 4 windows.
Turns out that my wife had accidentally lowered her front passenger window ever so slightly. Completely closing the window immediately solved the problem! The window couldn't have been lowered more than an eighth of an inch, and wasn't visually noticeable.
Hope this helps.
2014 Deep Cherry Summit 4x4, 5.7