When Your Furnace Talks, Listen: 14 Sounds That Require Attention

It may be that you have a problem with the motor, or it might be a bearing in the motor that is making the noise.

The blower wheel of the fan may be out of alignment. Wiggling it could potentially solve the problem, but you should also check that the mounting plate is not warped and rubbing against the blower wheel. As well, check that the motor mounts are not loose and the bearings are in good shape.

It is more than likely the metal parts to your furnace cooling down. However, it may be something more serious, like a leak in the heat exchanger, which can result in carbon monoxide leaking into your home, so you should call a furnace service technician.

The problem is probably in the pipes, rather than the furnace itself. This may be caused by the contraction of the pipes when the furnace turns off and the pipes cool down.

This sound may lead to the ducts, which can expand and contract in cold weather, especially if the basement is not heated. It might also indicate a problem with dirty burners in the furnace. By process of elimination, you can determine that it is not the ducts or the burners. It may be that your gas valve is defective, which can cause a delayed ignition. In most cases, it is wise to call a service technician.

This sound may indicate a problem with your furnace and a technician really needs to check it out.

This may come from the furnace burner’s light when temperatures dip outside. You can eliminate this noise by turning the off/pilot/on control to reduce the burner flame.

It might be a motor bearing.

This sound indicates a cracked belt.

If it sounds like metal on metal, you may have a loose or broken part. Please call a service technician.

A clanging sound, and then doesn’t light can mean a leaking gas valve or loose wiring.

This could indicate that the burners are dirty or your pilot light may need adjustment.

When the return side airflow is blocked from a clogged filter, a substantial pressure drop occurs, which can cause the duct walls to shake, knock, or vibrate.

A correctly-installed vibration damper is necessary to prevent the blower compartment or air handler from making knocking noises or sending all sorts of other noises through the ductwork.