1991 Buick Century

The blower motor's bearings are bad. A replacement motor and fan are surprisingly inexpensive. You can unscrew it from the housing pretty easily, too, under the hood near the firewall on the passenger side. But you'll probably have to remove the power steering pump from its pedestal (three 13mm bolts through the holes in the pulley and one on the back brace) and push it aside for clearance.