whistling in cabin when fan is on

[laserb5s47]

hey guys, new to forums

what causes the loud whistling noise near passenger side vent when the fan is on? the whistling goes away when fan is off

thanks

[Blue_S4]

could be a bad fan. maybe one of the blades is chipped or cracked or busted. that would explain some whistling.

[Rajan147]

hitting/grazing the bi-pipe?

[laserb5s47]

i was told it might possibly be the pollen filter? is this a possibility? how much for this part and how hard is it to replace?

thanks for the input guys!

[Rajan147]

cabin filter?

http://www.audiworld.com/tech/misc36.shtml

[therox182]

if it happens when you're heat is on, it may be the blower motor that's behind the glovebox. Mine used to squeak while the heat is on, and oddly enough, when I would be turning left. I just took the motor out and sprayed some WD40 on it and the sound hasn't come back since.