If your evaporator motor is sqealing or making a grinding noise while running, most likely there is a problem with your evaporator motor or evaporator blower wheel.The motor could be going bad due to the bearings going bad. Sometimes though the evaporator blower wheel can comes loose and can start rubbing against the squirrel cage housing. Another situation is were the blower wheel itself starts to come apart and starts rubbing on the housing. In some cases the inner part of the blower wheel will spin not spinning the louvers causing a squealing noise. A service technician should be called out to determine the cause of the noise.