Your HVAC system is bound to make some noise when it runs, nice quiet ambient noise. However, when you start noticing sounds that don’t seem quite the norm, there may be an issue you need to address. The guide below will help you self-diagnose some of the most common HVAC-related noises you may be hearing in your home, and help you figure out how soon you need to call in the experts.

Uh, what’s that scraping sound?

It’s the sound that says, “turn off your system right away.” If a scraping noise is coming from the fan, it may mean it’s being obstructed by some foreign object. A warped or broken fan blade can crush the fins and tubing on your condenser coil, eventually leading to a refrigerant leakage and decreased efficiency. Inspecting fans for damage should be a regular part of HVAC maintenance.

Things that go thump in the night

Whether it’s night or day, a thumping noise like an out-of-balance load in your laundry machine drum, usually means the motor or a blower wheel is out of balance. It’s best not to ignore it because it could cause a ripple effect of other problems down the road.

Shake, clank, rattle, and roll

It’s true — your HVAC system sometimes gets rattled. Twigs or other debris can get inside the fan of your outdoor unit and cause some rattling. If you see that is the problem, cut power and remove the debris. If you see it has caused damage to the condenser coils, compressor, or fan, call a technician. Other times rattling could mean the fasteners to the metal housing have come loose and can be easily tightened. If it’s clanking, however, parts could be loose, and you definitely need to call a technician.

Pop! Goes the ductwork

If you hear a loud pop or bang when the system fan starts and stops, it could be your ductwork reacting from the negative pressure of the fan; the fan shuts off, pressure releases, and the ductwork pops out. It could mean you have an undersized or flimsy duct, some closed vents, or a clogged air filter.

Something is hissing at me

It’s not anger, it’s escaping air. If it’s a light hiss, it could be coming from your air vents because your filter isn’t installed quite right or is the wrong size. It could be too many vents are closed off or furniture is blocking airflow. If it’s a loud hiss coming from the walls, you likely have a duct leak — which wastes heated/cooled air that should be circulating inside your rooms, not inside the walls. If this is the case, you need to call a technician. If it’s more of a whistle than a hiss, you could have a refrigerant leak in your condenser, or something else is causing internal pressure. This could be extremely serious, and you should contact an HVAC company with 24-hour service to address this right away.

Remember, some noise is good because it means your system is working! A little squeal or thump when your system cycles on may simply indicate you’re due for a tune-up. But when it becomes loud, annoying, or disruptive in any way, it’s time to call in a professional to determine which sounds are normal and which are a cause for concern. Sometimes it’s just a matter of adding some lubricant, tightening parts, or replacing belts, but knowing the difference can sometimes be difficult. Acting promptly is always a good idea and could save you money down the road in repairs and early replacement costs.

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