5 Common HVAC Sounds & What They Mean for Your System

Sometimes, with older HVAC units, you may be able to hear when the system starts up. But if the sound is loud enough to stop you from your latest TV show binge-watch, the problem may be more serious.

When an HVAC unit is working properly, it is relatively quiet. If yours is communicating with you through a series of clangs and whistles, it may be asking for help.

Listen closely to what sounds the unit is making to determine the source of the problem. The five most common sounds and their likely causes are listed below:


If you hear hissing, it indicates a leak in the system. If it sounds like the air is escaping into your walls, it is most likely a leak in your ducts. These two problems are minor and can be easily fixed. But, that means the air that should be cooling your home is now cooling the inside of your walls. So, the longer you wait, the higher your energy bill will be.


If you hear popping, it is most likely the metal in your system contracting and expanding with the changing temperatures. Although this sound is normal, it can be bothersome to some homeowners. Consider installing additional insulation to muffle the level of noise, while your system is running.


If you hear clanking, it could indicate loose equipment inside the unit (i.e. loose pipes, loose blades, etc). This is a serious problem because a loose part could collide with other operating systems, causing major damage or the need for an expensive replacement if the unit stops working. Reach out to an ALPS representative right away, if you are concerned.


If you hear squeaking, it is most likely coming from the motor. This may indicate a worn or malfunctioning fan motor and/or indoor blower motor. Some units will make this sound when they start up after a period of hibernation, but if the squeaking persists, you should schedule an appointment to find out if you need a repair or replacement.


If you hear a high pitched whistle that sounds like a scream, immediately turn the unit off and contact an HVAC technician. The system could be experiencing high internal pressure within the compressor or leaking refrigerant fluid. In either case, the problem can cause major damage to your HVAC unit, and depending on the problem, could negatively impact your family’s health.

If you’re unsure about the noises coming from the A/C, let us know! Our technicians can help you identify the source of the problem and find the best solution to fix it. Please call 800-994-2577 or visit our website to schedule an appointment.