Furnace Blower Vibration

Blower Wheel Setscrews

• One common cause of vibration from the furnace blower is when the setscrews on the blower wheel work themselves loose. When the blower turns on and while it operates, these loose setscrews could be the source of the vibration, and will eventually lead to damage within the blower. This will also result in poor airflow through the HVAC system. To get rid of this problem, ensure that the blower wheel is in balance, and tighten the setscrews on it.

Slipping Pulley

• Some furnace blowers are belt-drive models and use an adjustable pulley. The tension on the pulley belt should be loose enough that the belt pushes down about 1 inch when you press down on it with your finger. You might notice vibration if it is too loose, to the point where the belt slips. If you find that the belt needs tightening, loosen the setscrews and adjust the distance between the blower pulleys to give it more tension. Also, check the condition of the belt, and ensure that it isn't frayed or missing parts out of it.

Blower Motor

• The blower motor itself might be vibrating. Some blowers have oil ports, and if the motor bearings are not properly lubricated, the motor life is shortened. Follow the furnace manufacturer's instructions to apply the right amount of SAE-10 nondetergent oil into the blower's oiling ports, at the start of every heating and cooling season. Also, ensure that the mounting bolts beside the motor are tight. Use either an adjustable wrench or a socket wrench to tighten the bolts, if necessary.

Dirt Buildup

• Dirt will also build up within the blower wheel, which will not only restrict airflow, but will also cause vibration within the blower. To prevent this, don't run the furnace while it is dirty, but make sure you check the blower wheel for excessive dirt and blockages on it. Turn off the furnace before doing any work on it. Wash the blower wheel with a rag dipped in soapy water, and dry it off.