What’s this Noise My A/C is Making?

Man listening to air conditioner

If you’ve ever heard a new a/c unit running, you may have noticed that modern units are much quieter than those of the past. But did you know that premium tiers actually have sound dampening technology which can keep sound levels below 55 decibels?

While decibel levels do vary from unit to unit, a lot of ruckus coming from your system is not normal and should not be overlooked.

Ignoring a noise from your HVAC could turn a small issue into a larger one that will cost more to fix or replace. Figuring out what is happening with your unit as soon as possible will help to make sure that no problems are exacerbated over time.

So, what could these mysterious signs be? Check out our guide below to try to decipher. Remember, this is just a guide and most likely, you will need to call your State Certified HVAC contractor to look further into the problem. Turning off your unit upon hearing any unusual sounds is the best way to prevent any further damage until you can have it looked at, so make sure your unit isn’t still running while you read this!

So now that you’ve turned off your HVAC unit, and are hopefully sitting comfortably in some air conditioning at a nearby cafe, let see what may be wrong:


All pieces are tightly secured inside of an HVAC unit when it is manufactured, so if you hear a clanking sound, that’s a good sign something has come loose. Nothing should be able to rattle or bang around when everything is properly in place. Your indoor blower or outdoor fan may have come loose and is hitting other parts nearby, or a piece may have fallen to the bottom of the sealed unit. You can imagine how if you ignored this issue, the fan could cause more damage than there initially was over time.


A bang is another sign that something is loose. Banging noises are frequently associated with blower motors and are a good indication of worn bearings. The good news is, repairs like this are far less expensive than replacing a compressor and can be fairly quickly remedied.


On some HVAC systems, you may hear a squeal when your fan gets going. If the sound continues after startup, there is definitely a problem. When a fan motor or a blower motor is going out, they can squeal loudly.


Yes, many of these sounds are caused by something loose inside your system.  But the difference in each sound could mean a world of difference in what is happening to your HVAC. A rattling sound could just mean that your entire unit is loosening (kind of like a house settling). If this is the case, you actually can do something to try to remedy it yourself. If it is your unit loosening, it could be helped by ensuring all of the screws on your casing are tightened.


You will probably know right away that there is something wrong if your air conditioner turns on and it starts screaming! Turn it off right away, to save your ears and your air conditioner. This sound is usually caused by high internal pressure in your compressor. When this occurs a sensor may trip and cause your unit to turn itself off, which is good as it’s designed to do this for safety. If you hear this scream, you will definitely want to call your State Certified HVAC contractor right away.


Normally, when your system starts up and shuts off, you may hear a few clicks as it operates. These sounds are most likely normal but if you believe these sounds to be of recent development would be advised you have a technician examine the system for potential causes before they become serious problems.


Clanking could mean that debris has gotten inside of your unit. While AC systems are closed up tightly, it’s still possible for dust, leaves, or pests to get inside. The copper lines from outside to inside could also be vibrating against something and should be examined.


A humming sound is sometimes less serious than the other sounds we’ve discussed. It is often caused by an electrical problem. If your machine hums but doesn’t start, there could be a motor issue. Another cause for humming or buzzing could be a loose part that is vibrating against something else inside of your HVAC system while it is running.

In conclusion

Your HVAC system is an important part of the comfort of your home. It is a costly item to have installed, so should you hear any sounds you are unfamiliar with coming from anywhere in your system, you should definitely check it out as quickly as possible. Neglecting to investigate the source of the sound could result in further damage being done to your system that will cost much more to repair or even replace! When in doubt, it’s a good idea to turn off your unit until you can call a State Certified HVAC contractor to come out and inspect it.

Also, remember that scheduled maintenance of your system twice per year by your contractor will ensure that everything is kept clean, tightened up, and running beautifully for years to come. For more on information on maintenance please check out our article: Do I Really Need HVAC Maintenance Twice a Year?


Contact Us

  • This field is for validation purposes and should be left unchanged.
Call Now Button