AC Noises – How to Know When it is not Working Properly

Woman using ductless air conditioner

Air conditioners are designed to run with as little sound as possible. Unless you are sitting directly under a vent or the unit is directly outside your window, you shouldn’t notice when it comes on or shuts off. However, if you are hearing things go bump in the night or notice other unusual noises throughout the day, don’t call Ghost Busters until you consider that it might be your AC telling you it needs attention.


Unlike the Seven Dwarfs, air conditioners should not whistle while they work. If you hear whistling, see if you can locate the source of the whistle before you call an HVAC contractor. It could be that something has become caught in a vent somewhere and can be easily removed.


Hums are a bit trickier than whistles. Your refrigerator hums and it means it’s working. There is a difference between the hum of a motor and the hum of a vibration. If the hum is a new noise, it could be the sign of some ductwork that has come loose and is vibrating. It could also indicate a loose part in the motor somewhere. If you are unable to find the source of the noise, or if you cannot see what might be causing the noise, give your HVAC contractor a call to be on the safe side.


Your air conditioner will not ever literally sound like it’s hiccuping. (If it does, it definitely needs our help… and its own YouTube video.) However, if the AC sounds like it’s stuttering or having difficulty running consistently, you probably need some professional eyes, ears and hands to properly diagnose the problem. The motor could be going out.


A shrill squeak when the air conditioner motor engages is a sign that there may be a loose belt or a belt on its last legs. Replace the belt or call your AC repair contractor to do it for you.


Rattles are essentially hums with an exclamation mark. If you hear rattling in the AC unit, it likely means there are loose parts or something is interfering with the fan. Get it fixed sooner rather than later to avoid additional malfunctions.


The grind of metal on metal is as shiver-inducing as a fingernail on a chalkboard or aluminum foil on a dental filling. Grinding sounds from your AC may mean that your bearings need to be replaced, that a part has come loose or that the motor is dying a slow and painful death. As with a rattle, repairs should be made sooner rather than later. You don’t want to get caught without cool air in your home.

Silent But Hot

If your air conditioner is not making noise, but it is not producing cold air either, you may need to check to make sure you have enough refrigerant and that the compressor is actually working. As with all of these problems, feel free to call the professionals at BlueAir Heating and Air Conditioning for an expert diagnosis and repair.

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