Why is My AC Making Noise?

Portrait of concerned young girl with hand to ear gesture carefully listening

Your air conditioning unit will always make some noise when running, and older units are typically louder than newer ones. Consider the age of your unit before getting too concerned about the noise that it is making. At Arise, we recommend a maintenance inspection at least once a year to inspect the health of your air conditioner. If the regular noise level from your AC or Heat Pump unit is annoying, talk to one of our technicians for advice on what steps may be taken to reduce the noise level.

Here are a few things to consider if the noise your air conditioner is making is unusual or is different from its regular hum.


The most common rattling sound comes from a filter that is not installed properly. The noise could also be from something that has fallen into the vents or from a loose bolt, screw or fastener. The outdoor large motor, the compressor, could make a rattling sound. If this is the case, a professional technician should definitely evaluate the noise.


Most likely this noise is caused from one of the fan motors, fan blade or blower wheel. It could also be worn bearings.


There are several internal parts that can make these sounds when failing. Vibration of failing parts, or parts rubbing together can also create these noises. Because of the electrical voltage present, do not try to identify the cause of these noises yourself. Call our trained technicians.


This noise might be coming from your duct work when your AC unit turns off and on. This usually indicates a problem with your duct work and not necessarily a problem with your central air equipment. Duct work ages just like other other things and require routine inspections to ensure it is functioning effectively.


Your ductwork or filter grille may be the cause of this noise due to air leaks. Refrigerant leaks can also cause hissing sounds. Potential refrigerant leaks should be checked by a professional technician.

A few other questions we may ask when you call in to request service are:

1) Is the noise coming from the outdoor unit, the indoor unit or the vents and registers?
2) When the unit is running, is the noise intermittent or constant?
3) Did the unusual noise begin suddenly or build over time?

Your air conditioner is a piece of machinery with many moving parts and circuitry and, like a car, it requires regular maintenance by experienced professionals to identify diagnose and remediate problems. Trust your ears. If your air conditioner or heat pump is making a noise that is new, unusual or harsh, call us today at 512.267.5000 or schedule service online.

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