Alarming Furnace Noises and What They’re Telling You

Don’t allow yourself to experience a catastrophic furnace breakdown during a cold winter night in Lakewood Ranch, FL. Here are four alarming furnace noises and what they mean:


Clunking indicates loose parts knocking against one another. You might have a misaligned fan that requires a service technician to tighten it during your next maintenance appointment.


You’ll notice a whistling sound whenever something obstructs the HVAC system’s airflow. An object stuck inside the ductwork or a blocked return might be the cause.

Closed vents or dampers cause whistling noises. A dirty air filter is another culprit because it means that dust, dirt and debris are restricting the airflow.

Your furnace will also whistle if it’s too large for your home. If you’ve replaced the air filters and still hear whistling, schedule an HVAC maintenance appointment to learn if you might need to consider a new furnace installation.


A screeching or scraping sound inside your HVAC system reveals that one metal part is scraping against another metal area of the furnace. One possibility is a loose drive motor that’s vibrating and causing the unsettling screeching noises.


Ductwork consists of thin metal. Banging noises might be nothing but the result of this metal material expanding and contracting during the heating and cooling process.

The electronic ignition system could cause banging sounds as the furnace cycles on. In this case, the culprit is often a low gas pressure situation. Gas builds up over time and results in a banging noise upon ignition.

Don’t allow a banging noise to persist. Call in professionals to service your furnace and find out if the ignition system requires repair.

Other than changing the air filters, don’t try to fix your furnace by yourself. Contact Custom Air & Plumbing to arrange your next furnace maintenance appointment.

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