I'm getting confused because I think we're talking about two different fans.
There is an auxilary fan in the kick panel under the dash that Turbodiesel is talking about.
The other fan is the aspirator fan is right directly underneath the passenger air vent, just to the right of the glove box.
I don't know which one is actually making the squeaking noise, but I think it's the aspirator motor fan below the air vent.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".