A/C whistling

Sometimes when running the a/c, it makes a really loud whistling noise, other times not...it's a very high pitched whistle, and ceases when the a/c is turned off. I'm hoping its a leaf or something in the cabin/vents and will check once the rain quits. Any other ideas?

 

mine does that so if you figure that out, please let me know. but mine seems to get louder when I push the gas pedal

 

I notice it especially when I put it on High...not so much on the first 2 of 4 speeds. Doesn't seem to affect the airflow or coolness. Any one else?

 

Is one of your vents closed or maybe clogged? Mine whistles when the AC is on high and one vent is closed. When I open the vent it stops.

 

Mine does it on medium-low to high speed, but never the lowest setting.

 

Mine does it on high so I bought a used blower motor thinking it was a bad bearing. Waste of money, still whistles on high.