Furnaces are notorious for making strange noises during operation, particularly after years of use. While not all of these sounds indicate a major issue, you should call a professional anytime you hear something unusual coming from your furnace. Let’s take a look at some of the more common warning noises that can come from your furnace, and what problems they can indicate.
A grinding noise coming from your furnace indicates that the bearings in your air handler motor are wearing down. The air handler is the section of your furnace responsible for the circulation of warm air throughout your house. The air handler motor is what turns the fan and keeps the air circulating. Inside the motor is a group of bearings, designed to lubricate the motor and keep it running smoothly. Over time, however, the bearings can lose their lubrication. This actually increases the resistance on the motor, causing it to eventually overheat and burn out. If you hear grinding coming from your furnace, you should call a professional immediately before you have to replace the motor.
Squealing coming from your furnace is also often located in your furnace’s air handler. The motor is connected to the fan by a rubber loop, called a “fan belt.” This belt is responsible for the transfer of motion that makes the air handler fan turn. Over time, the fan belt stretches and cracks, creating more friction between the various parts of the air handler. That is what creates the loud squealing noise that you can hear when your furnace starts. If not treated right away, the fan belt will break and render the air handler unable to operate.
A banging noise can actually have a couple of different causes. It could be your ducts expanding and contracting from the hot air running through them, which isn’t a big deal. It could also be due to part of your burner assembly firing late, due to carbon build up on the burner itself. That is a big deal, and needs to be treated. You’ll need to call a professional to confirm the source, one way or the other.