CPS discusses what Massachusetts homeowners should do when their furnace makes noise.

If your furnace is making unusual noises, we understand it can be alarming (pun intended!). Knowing what falls under “normal” and what might be cause for concern can be helpful when this issue inevitably arises. It is important to note, if you are ever unsure you can always call us.

Some common noises that furnaces make are banging, whistling, buzzing, clicking, and rattling. Each of these sounds happen for specific reasons, so it is helpful to have some basic knowledge of causes. Knowing what is typical and what is cause for concern can help you quickly evaluate your next steps, if there are any, when this situation arises.

Noises that may come from your furnace include:


This sound indicates that either your furnace’s gas ignition is delayed, or your air ducts are expanding and contracting. You’ll know that your furnace’s gas ignition is lagging if the sound is coming from the unit itself. However, if you hear these sounds all over the home, it’s a duct issue.

If the furnace itself is making a banging sound, it’s of the utmost importance that you call CPS immediately. The gas build-up in the furnace can cause an explosion that will damage your unit. One of our technicians will diagnose the root of the problem so that it can be remedied.

If the sounds are throughout the home, the issue is less urgent. We would recommend contacting us to have your ductwork inspected. However, in the meantime, you can check to make sure vents aren’t obstructed by furniture or other items and change your filter.

Only a licensed HVAC technician make a diagnosis of a furnace or HVAC unit issue.


This sound is usually no cause for alarm. In fact, you can probably fix it on your own. Changing your air filter, cleaning your vents, and removing obstacles around vents to ensure air can flow freely through your ductwork should solve the issue. However, if the sound persists, please give us a call so that we can ensure that your ducts, vents, and filter are clean enough to allow for proper airflow.


If you hear a buzzing or humming sound from your furnace, this is another instance when you’ll want to contact us right away. This sound indicates an electrical malfunction. To ensure your safety and prevent damage to your system, a trained professional will be required to assess this issue.


This indicates either a broken motor fan or, more commonly, a faulty ignition. In either case, a professional is required to diagnose the issue. When your furnace ignition isn’t working correctly, it could cause your system to stop heating your home.


If you hear this sound, ask us to send a tech. There could be a part loose which we can tighten up for you, or your heat exchanger is cracked. We should warn you; this may be an expensive repair. When a heat exchanger is cracked , sometimes the cost of fixing it is comparable to buying a new furnace. However, the upside of this is that you may be able to choose a more durable and efficient model. A newer system saves our customers more money in the long run.

It is important to note that the issues we discuss in this blog are common reasons for furnaces to make sounds but only a licensed HVAC technician should be making a diagnosis of the issue. Having regular maintenance tune-ups allows for issues to be detected early and usually dealt with before serious complications arise.


We hope you found this article helpful, and we look forward to continuing to ensure your comfort and safety. We thank you for choosing CPS.

If you are currently in need of a repair, you can reach us at 508-460-6691 or fill out this form.