Common Furnace Problems: Noises

Date: October 30, 2018

Discerning noise

Through the rest of fall and all the way through winter, there will be various sounds that you may hear from your oil furnace. As with any mechanical device, many of the sounds you will hear will be perfectly normal. It’s just your furnace doing its job.

But it’s also important to know which sounds are normal and which ones are not. Here is our advice: the next time your furnace turns on and starts generating heat, listen for the sounds it makes and observe how long the sound generally continues. By doing this, you’ll be more aware of any noise that’s different or rather odd. In other words, a noise you’ve never heard coming from your furnace before may indicate a problem.

To help you distinguish between minor and major problems, here is a list of common sounds you may hear from your furnace. Please be advised that these are only general guidelines and presented here for educational purposes only. A correct diagnosis can only be made after a system inspection by a qualified oilheat technician. (This is just one reason why it’s always a good idea to get your furnace checked at least once a year).


This usually comes from the transformer; all transformers hum to some degree. If the humming begins to increase, it’s an early signal that the fan motor may be wearing out. Immediate attention is not required but an inspection should be done soon.


This often happens when the bearings in the blower motor wear out. If you hear this noise, shut off the system immediately to avoid further damage. Then arrange for service.


If it’s an older system, the blower motor may need oil. There may also be a loose belt.


The blower wheel or motor may need to be rebalanced.


This noise could mean that a dirty filter is constricting air flow.


Abnormal air pressure makes ducts pop in and out. This can be caused by a clogged filter, an undersized or flimsy duct, or closed vents.


When air gets forced through your ductwork, you may hear creaking noises because the ducts are expanding and contracting. This usually doesn’t happen with a properly installed variable speed system. There will be reduced air turbulence because the system doesn’t “blast” on and off.

If you have any concerns about the operation of your heating system, please contact your equipment service provider.