Whenever I turn on the fans full blast in my '93 100CSQ it makes this horrible squealing noise that is coming from inside the middle vents. If I close the two middle vents it will still occur but softer and it's heard from the two side vents. If I turn the fan down it will only happen when I go over bumps. It started ever since I blew pressurized air on the vents to clean the dust. Bad idea I suppose :\ Any suggestions on how to fix?

<center><img src="http://62.117.101.85/imaudivw/VAG02CBB.gif"></center><p>IF so, can you determine, by looking at it, whats needed to remove it?

Normally on most Audi's the fan is held in by a few screws.