Strange HVAC Noises and What They Mean | Columbia Heating & Cooling
Written by Columbia HVAC

Strange HVAC Noises and What They Mean

Does turning on your HVAC come with unexpected sounds? Perhaps a persistent humming or a clunk in the night? While not all noises are indicative of a problem, being able to identify those that are could save you from hefty repair costs.

To help you assess when to call in a professional, we’ve put together a helpful list of noises and what they could mean:


Hissing or a high-pitched vibration can signal a few different issues. If you notice the sound coming from walls, this could be a symptom of poorly executed ductwork. Improperly installed ductwork results in air leakage from your system – and wasted money on heating and cooling costs for you. If you suspect ductwork to be the culprit of a persistent hiss, call in a technician for help.

However, hissing doesn’t always require a professional. A high-pitched vibrating sound can simply mean your HVAC isn’t getting enough airflow. Check to see if your vents are open and unobstructed by furniture. If you notice a light hissing, make sure your air filter is the right size and set snugly to avoid air traveling around the filter rather than through it.


Rattling is especially common in outdoor units. Small branches, leaves, and other forms of debris can slip through the grate and into your system. You can resolve this issue yourself by turning off your HVAC and removing the debris. If the rattling is coming from an indoor unit (especially one with visible damage), avoid running it until a professional can take a look.


Clanking sounds can equate to expensive repairs. If you’re HVAC is clunking and clanking – pipes, blades, fans, or other metal parts may have become loose. Loose parts bouncing around and grinding against one another is bad news for your unit and requires the expertise of an HVAC professional.

Should you notice a soft humming or wooshing of air – have no fear. This is simply the sound of your HVAC bringing in air or coming to life when you turn it on. Alongside humming, you may hear a quick squeak or thump upon switching the thermostat. These noises are not cause for concern and are typically resolved with a tune-up.

In effort to save you time and money, we recommend getting familiar with your HVAC unit. Knowing where your system is located, how old it is, and when it was last serviced can help you troubleshoot any issues more efficiently and effectively. Schedule routine maintenance and switch out your filter (we recommend once every 3 months) to prevent strange sounds and costly surprises. Should you ever hear a clank, hiss, whistle, or rattle, the technicians at Columbia Heating and Cooling are ready to help! Your comfort is our priority.

Give us a call today for a FREE replacement quote at (503) 624-2704.