There is a loud whine or scraping sound especially when the 11 year old Furnace Blower Motor/fan starts up. With power off, when I turn the blower motor fan blades by hand they make a scraping high pitched sound in one direction, but not the other direction. The problem started suddenly during a cold spell. Can I tell if this is a motor bearing, fan alignment or other problem without taking the fan assembly out of the furnace?
Turn off the electrical power to the furnace and then take the blower door off the furnace. Reach into the blower in the end opposite the motor and try to wiggle, lift or other wise move the blower fan up and down. if it moves up/down you could have worn motor bearings. If it doesn't move then try as @George Anderson wrote. If this is an older unit the bearings could be in need of lubrication. Note, that some motors can not be lubricate which would indicate a need for the motor to be replaced. Hope this helps.