The part(s) or condition(s) listed below for the symptom Furnace is noisy or loud are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
The blower wheel blows air out of the furnace and through the house. The blower wheel is attached to the blower motor shaft with a set screw. If the set screw is loose, the blower wheel will wobble on the motor shaft, and the wheel will be noisy as it turns. Check the set screw to ensure that it is properly tightened. Next, inspect the wheel for damage. If the blower wheel is damaged, replace it.
Over time, the bearings in the blower motor wear out, causing the motor to become noisy. Some furnace motors can be lubricated—if your furnace motor can be lubricated, try lubricating it first. If lubricating the motor doesn’t solve the problem, or if your motor can’t be lubricated, replace the motor.
The draft inducer motor draws air into the burner and then exhausts it out the flue. If the motor bearings are worn out, the motor will be loud. If the draft inducer motor is unusually noisy, replace it.
The draft inducer blower wheel blows air through the burner system. Inspect the blower wheel for damage (such as a separated center hub or broken fins). If the blower wheel is damaged, replace it.