Six HVAC Noises And What They Mean

HVAC systems have a reputation for being noisy, especially if they are not well-maintained. Oftentimes this is an annoyance inside your facility, but some noises can indicate a true issue in your system. If you notice any of these six noises, it may be time to contact your MaintenX technician and schedule a consultation: 

Loud humming or clanking. 

Most HVAC units will make a quiet humming noise, especially if the A/C is working hard. However, if this sound becomes louder than normal or if it sounds like something is moving around inside, there is most likely an issue. Loud humming or clanking noises could indicate:

  • loose parts, such as the blower motor fan, loose blades, 
  • loose pipes that are rubbing together
  • of loose wiring, circuit breaker overload or 
  • failed condenser fan motor.


This noise can mean one of two things. Squealing can be common upon startup for some units, so if you’ve heard this noise before you probably don’t need to worry. However, squealing can also be a sign of a failing fan motor, blower wheel, or ancillary fan component. This sound could mean imminent failure throughout the system if you do not address it promptly. 

Outdoor ratting. 

If your outdoor unit is making a rattling sound, it is likely that a piece of debris has been caught in the fan. While the metal grate around the exterior will protect your unit from large sticks and leaves, smaller pieces of debris can get inside and damage your fan. You may be able to shut off the unit and remove the debris, but if you see any sign of damage you should call your HVAC technician for a consultation. 


Sometimes HVAC units will click when they start up, but if this noise is continual it could be a sign of an electrical problem. Some of the controls and components that control the thermostat may click when they become faulty, so if you hear this noise always consult your HVAC technician. 


If you can hear a hissing noise, your ductwork is most likely leaking air. While this isn’t an emergency, it is costing you money in inefficiency. If the hissing noise is loud, contact your HVAC technician as soon as possible. If the hissing is quiet, it could also be caused by an air filter that is not properly placed. Check your filter to make sure it is fitted snugly and is not allowing air to escape from the corners. 


If you hear a loud whistle or scream-like sound coming from your HVAC unit, you should turn it off immediately. This noise typically only happens if there is a refrigerant leak or if the internal pressure in your compressor is too high. Both of these are highly dangerous situations and need to be addressed immediately. It is likely that your HVAC system will shut off on its own due to sensor recognition of the problem, but if not, shut off your system and call your MaintenX repairman. We can help you fix the situation and ensure your facility is safe. 

If your HVAC system is experiencing any of these issues, MaintenX is here to help. We specialize in HVAC repair and preventative maintenance, and can help you get your HVAC unit back to running at peak performance. For more information on our services, call your local MaintenX team today!

Leave a Reply

Your email address will not be published. Required fields are marked *