Your furnace contains bearings in the fan motors, which aid with the smooth functioning of the motor and fan. Failure of these bearings can lead to extensive damage throughout the entire furnace assembly.

Failure Signs

One of the first signs of failing bearings won't be a lack of function or heat, but instead a loud noise. As the bearings begin to fail, friction causes the bearings to become noisy. Generally, this noise is a vibrating sort of hum or a grinding sound. The noise will only be present when the furnace is running, and it may not persist for the entire furnace cycle. If the problem isn't addressed, the noise will worsen over time.

Eventually the failing bearings will impede the operation of the furnace. Since bearings impact the operation of the fan motors, reduced airflow is one sign of impending failure. The fan may be slow to start, or it may begin moving more slowly or intermittently. Eventually it will seize up completely and there will be no airflow from the furnace.

Cause and Concerns

Bearings fail due to age and lack of lubrication. Bearings need to remain lubricated in order to move freely, which in turn allows the fan in the air handler to move freely. If this lubrication wears off or becomes dirty and gritty, then the bearings will stop moving. Often, bearing failure is either the result of a failure to perform regular maintenance and lubrication or it's a result of overheating in the furnace motor damaging the bearings.

The main concern is the fan and fan motor. If the bearings aren't working, then more stress is put on these components. The additional stress and friction can drastically shorten the life of the air handler motor and fan.

Prevention and Repair

Fortunately, bearings can last the life of your furnace if you take care of them correctly. Schedule an annual furnace maintenance call. At this time, your technician will repair any minor issues that could be causing the fan motor to overheat. They will also fully lubricate the bearings and moving parts of the air handler, thus preventing problems.

If the bearings are already damaged, there are two repair options. If the motor is undamaged or repairable, then the bearings can be removed and replaced with new ones. If the motor is damaged beyond repair, then the entire air handler motor assembly will need to be replaced.

Contact a furnace repair service if you suspect that bad bearings may be causing issues in your furnace.