Looking at the Different Types of Furnace Blower Noises and What They Mean

Irrespective of the age of your HVAC system, it can develop problems at any point in time. When your unit is operating normally, the sound it produces is different from when there is a problem. Whenever you notice your HVAC system emitting sound or noise that is suspicious, ensure the matter is addressed urgently because it could be pointing to a much deeper problem. This post discusses the different types of furnace blower noises and how to tell them apart.

Screeching or Squealing

Squealing noises coming from a blower motor may indicate bearing problems or a bad belt. Usually, belts snap after sometime due to wear and tear. This is why as one of the maintenance procedures, belts are supposed to be checked regularly so that where necessary they can be replaced before they break. For the bearings, they should be lubricated to reduce or eliminate the noise they make when the motor is rotating. Adding a lubricant isn’t a difficult task as long as you know how to put the correct oil. Don’t use lubricant products such as 3-in-1 or WD-40 oils. These are lightweight and will not serve the purpose. Oils such as SAE-10 are the best for this operation.




Clunking, Banging, Thumbing or Loud Rattling Noises

Whenever you hear your furnace blower producing such sounds, the problem is normally the motor or blower assembly. Rattling noise indicates a loose component within the system which should be identified and repaired with urgency before or breaks or completely disconnects. Banging sounds on the other hand indicate a broken or disconnected component. When you hear this sound, immediately shut off the system if your blower is running. From time to time, the motor mounts on the assembly may become loose or the blower may be out of alignment. Ensure the motor assembly is inspected by a qualified HVAC technician.


When the blower is running and you hear this sound, chances are high that something is stuck in between the blower blades. Alternatively, something inside the housing unit could be interrupting the blower while it’s running. This sound can best be described as that produced when playing cards are attached to the spokes of running bicycle tires. While this noise may be ignored at some point, the best way is to have the unit inspected because the component creating resistance may easily wear out the motor.

Repeated Clicking Sounds

When HVAC units turn on and off, clicking noises are common. However, when these sounds are repeated and coming from the control panel or the outside compressor, there could be a problem with a relay. An electric control may also be the cause of the relay failing and timing out.

Rattling Noise from the Fan Unit or Outside Compressor

When the fan turns on in the compressor unit, it shouldn’t rattle, but rather rotate freely. Whenever you hear a rattling sound within the unit, it is an indication that there could be a failing motor or a loose hardware. Never ignore this sound especially when it grows louder.

All the noises discussed above are typical of HVAC systems but they must not be taken for granted. It could be the only best way the HVAC system is communicating an internal problem.