5 Strange Sounds that Signal Trouble with Your HVAC

Bump! Bang! Buzz … “Well, that can’t be good,” you think. Slowly you approach your heating unit to listen closely, hoping it’s nothing too serious. Here we will walk you through five strange sounds your HVAC unit could make this winter, what they might mean and when to call a licensed HVAC professional.

What does it mean if my HVAC hisses?

If your HVAC makes a hissing sound, that can be normal if the heat pump’s outside unit is in defrost mode. But, if the hissing seems to be coming from the ductwork inside your home, then it’s most likely a leak that is letting air escape. That leaking air can lead to higher energy bills as the unit keeps running longer than is typical to compensate for the escaping warm air. A unit that works harder will need repairs more often and more frequent maintenance. Plus, air won’t be traveling easily through your home, leaving some rooms much cooler than others. You will need a pro to find, inspect and seal the leaks in tough-to-reach spaces.

What does it mean if my HVAC makes a popping sound?

If your HVAC system uses sheet metal ductwork, a popping noise is normal when the system first turns on. It is simply the metal expanding as the warm air flows through. Other times a popping sound can be caused when the fan turns on. The duct will pop inward from the negative pressure of the fan and then pop back out when the fan shuts off and releases the pressure. This can be caused by a clogged filter or closed vents, which you can remedy on your own. Other causes, such as an undersized duct or one constructed of thin, flimsy metal should be looked at by an HVAC service provider who can identify the cause.

What does it mean if my HVAC squeaks or squeals?

Weak or dirty bearings in the blower motor can be responsible for the noises, or it could be bearings that need to be lubricated. Squeaks and squeals could also be caused by a motor that needs lubrication or that is misaligned, but the situation can be as serious as a fan motor that is failing and needs to be replaced. Belts that are old, loose, or need lubrication are another possible culprit. With any squeak or squeal, turn off the unit and call a professional HVAC technician before any damage is done or before existing damage becomes more severe.

What does it mean if my HVAC thumps, bumps or bangs?

If your HVAC unit makes any of these strange sounds, turn off your system and call in the pros. It’s especially concerning if you hear metal on metal or a scraping sound. Something may be loose, broken or disconnected. The issue could be with the blower assembly, motor, fan blades or another part that a technician will need to diagnose.

What does it mean if my HVAC makes a buzzing sound?

If what you’re hearing sounds more like a hum than a buzz, it’s likely just the system running. Some HVAC systems are louder than others, which is no big deal unless the sound suddenly becomes louder, signaling a problem. If you’re hearing a buzz from your HVAC, that’s a reason to call an HVAC professional. There are many possible issues, so they will need to listen to the noise on site and visually inspect the unit. The cause may be a mounted transformer box that has become loose, it could be a problem with the capacitor or fan, or an unbalanced motor or blower wheel, to name a few possible origins. Please don’t wait to give us a call.

Contact Us to Learn More

Routine HVAC maintenance can help you prevent these problems from the get-go, so it’s wise to have two seasonal inspections and tune-ups each year. If you hear any strange sounds from your HVAC system this winter or if you have any questions at all, contact Fitch Services at 434-296-9980.