Noisy Furnaces: What Does That Banging, Clanging, Or Grinding Sound Mean?

When your furnace starts making more than the expected blowing noises, it's not usually a good sign. Different types of furnace noises can indicate different problems. Here's a look at three common furnace noises and what issues are often to blame for them.

Grinding or Scraping

Does your furnace sound more like a grinding wheel than a furnace? Maybe it's even making a scraping sound that reminds you of fingernails dragging across the chalkboard. Usually, sounds of this type can be attributed to issues with the blower wheel. The wheel may have come loose from its motor shaft, or it may have cracked completely. In most cases, these are not issues you can fix on your own without specialized training and knowledge, so your best bet is to call an HVAC professional. The blower unit or its motor will probably need to be replaced – though there's a chance a part may have wiggled its way loose and may just need to be screwed back into place.


Does your furnace make a banging noise when it turns on? The explanation in this case is pretty simple. Your furnace's burner is probably dirty, which delays the burners from igniting. By the time they do ignite, there's a bit of extra gas accumulated in the area, and it ignites with a banging sound.

If you have some basic DIY skills and don't mind getting your hands dirty, you can try fixing this issue yourself. Turn off the electrical and gas supplies to the furnace. Then, remove the metal housing from the burner chamber, and use a brush to brush off all ash and debris from the burner and surrounding housing. Wipe it off with a damp cloth, let it dry, and then put the housing back in place. Turn the electricity and gas back on, and with any luck, your furnace won't bang anymore.

Metallic Clanging

Do you hear noises like someone is tapping on a metal pan whenever your furnace is running? Are these noises most prominent once the furnace has been off for a while? This noise, most likely, is not coming from the furnace itself. Rather, it is caused by the ducts expanding and contracting as they are heated up and then cooled again. Having insulation placed around your ducts may help; it will keep them at a more consistent temperature. Your HVAC technician may also need to adjust the way the ducts fit together so that one does not bang against another when it expands.

For HVAC repair, contact a company such as Comfort Pros.