Why Is My Air Conditioner Making Noise?

Air conditioners and HVAC systems make a wide range of noises, because they’re large machines with a lot of moving parts that work hard to keep your home at a comfortable temperature.  However, sometimes a new or unusual noise will catch your attention and could be the first sign of a serious issue.

Common Sounds and Causes

All air conditioner units make noise when running.  Older units are often louder than newer units because designs have improved over the years to reduce noise.  So, if your older unit seems to drown out your neighbor’s newer model, it’s not necessarily a sign that it’s about to die on you.

An annual maintenance inspection by an HVAC professional will help keep minor noise issues in check, such as those caused by dirty fan blades or parts requiring lubrication.

Some noises, however, require more immediate action.  Contact an HVAC professional to expertly handle the situation.  A few common sounds are:

Rattling – if you hear a rattling noise coming from an exterior AC unit, it could be that something fell into the vents, such as leaves, sticks, or other outdoor debris.  A rattle could also indicate something as simple as loose bolts, screws, or fasteners.  However, the sound could also be coming from the compressor.  As the motor in the compressor begins to age, it may get louder and begin to make noises, which would be the first sign of a problem with it.

Grinding – If you hear a grinding noise, it is most likely one of the fan motors. The noise usually signals that something might be going wrong with the fan motors, such as a worn bearing.

Popping – Sometimes, you might hear popping noises in your ductwork, especially when the air cuts on and off.  This actually is an issue with your ductwork rather than the central AC unit.  As ductwork ages, just as anything else, it may also require maintenance to make sure that nothing is faulty or damaged, so that your AC unit can continue to effectively and efficiently cool your home.

Hissing – A hissing or whistling noise could also be due to a problem with ductwork.  However, a hissing noise coming from the AC unit itself is often indicative of a refrigerant leak, which should only be handled by an HVAC professional.


First, a homeowner should always make sure the AC filter is regularly changed.   Filters can become clogged depending on factors in the home, such as pet hair, excessive dirt, or cigarette smoke.  Keep an eye on the filter and change it when it appears dirty or clogged.  A good tip is to write, directly on the visible side of the filter, the date the new filter is installed.  That way you can start to get an idea of how much time passes between filter changes.

Second, the best way to prevent noises from occurring is to have your AC unit regularly inspected.  An annual tune-up will help keep minor issues from turning into major problems.

Finally, when your AC unit makes a loud, strange noise, it’s best to call an HVAC professional as soon as possible.  Your air conditioner is an expensive, complicated piece of machinery that requires a trained HVAC specialist to safely inspect and repair the equipment.

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