quite common. try removing heater motor and spraying bearings with wd40. if still squeals you need new heater motor. if you remove glovebox from vehicle, look from passenger side near top and towards back of black heater box, you will see a wiring plug going into round motor. undo wire and remove motor. motor may be secured by one screw on its perimeter or you may just have to turn whole motor 90 degrees to remove.
me
August 2009