The Different Noises An AC Might Make—and What They Mean

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The Different Noises An AC Might Make—and What They Mean

There was a time when air conditioners were noisy units; they rumbled and vibrated to bring cold air into your room. Of course, technology advanced enough to lead to much quieter AC units. Advanced compressors and sound-dampening technology exist to keep air conditioners almost as quiet as refrigerators.

However, your AC may still be making some types of noises or sounds. If this happens, you mustn’t ignore it. The sounds may indicate that something’s wrong, and your failure to act can turn a minor expense into a majorly expensive repair job.

So when you hear any of the following noises, turn off your AC and call an expert to check it out. Here are some of the more common noises an AC unit might make, and what such noises might mean:


This is a typical indicator that some part of the AC has been knocked loose or out of balance. Maybe the compressor itself has become loose, which may require a replacement to fix the problem.

Another possible cause for this type of noise is that the blades of your outdoor fan, or perhaps your indoor blower, have become unbalanced. They’re now hitting other parts of the AC as a result. This must be put back to where they were before, or else the problem can get bigger.


This is another sign that indicates a broken or loose part inside the compressor of the AC. It can be the crankshaft, piston pin, or the connecting rod. The indoor blower may also be unbalanced. Basically, to fix the problem you may need to replace the entire compressor.


Yes, a buzzing sound can be annoying like a mosquito that hangs out near your ear when you try to sleep. But the really annoying thing is that the noise can be cause by so many possible reasons:

  • There’s a refrigerant leak, so your AC is freezing up. If you have buzzing and your AC isn’t cooling, this can be the problem.
  • The blower is out of balance or damaged.
  • You need to change the air filter.
  • You have to clean the condenser coil.
  • Something is rubbing against the copper lines.
  • The fan blades are pout of balance or loose.
  • The outdoor fan motor is dying or loose.
  • There’s debris in the outdoor or indoor unit.
  • Some parts are loose.

You’ll have to address each possible cause to get rid of the buzzing sound. Of course, you can just let a pro do it for you.


It’s true that you hear electrical components clicking when you start them or shut them down. When they’re clicking regularly, however, it’s not normal at all. It may mean that your thermostat is failing or you have a defective control.


In the old days, air conditioners were expected to hum. Nowadays, it’s not normal though at least the sound isn’t usually about something seriously wrong. Nonetheless, it still indicates that something’s wrong.

There are several possible causes for the humming, however. Some of the wiring may have come loose. There may be problems with the motor. Electrical problems are possible too. The humming may be caused by vibration due to loose parts and refrigerant piping, and these problems can get worse if you let the humming continue.


If it sounds like you’ve pressed on mediocre brakes on your bike or car, then you have a problem. Some AC units can’t help but squeal when you start them up, so it’s not a problem when it stops. It’s only a problem when the squealing continues well after you turn the AC on.

Squealing noises can be caused damaged housing, a malfunctioning blower wheel, and worn down indoor blower motors and outdoor fan motors.


The first thing you need to do when you hear your AC rattling is to check the screws and bolts the AC casing. The rattling may have resulted in loose screws and bolts. You should also change your indoor air filter, and clean your condenser coils.

When there’s a rattling sound inside your AC, it may also mean that you’ve got some type of debris (like leaves and twigs) clogging up your AC. Something may also be wrong with the electrical contractor, and this can lead to damage in the compressor if allowed to go on unfixed. If the AC fan is loose, then it may be making the rattling sound.

In some cases, the AC unit may just be too old. Some of its parts are worn down and loosening and you may want to think about replacing the unit instead of just repairing it. Buying a replacement may actually be more cost-effective in the long run, compared to paying for frequent expensive AC repairs.

High-Pitched Whistling

This may even sound like screaming. Whatever you call it, it’s definitely a problem. You need to shut off the computer, and call a repair expert immediately.

The most common cause of the screaming noise is a refrigerant leak. This also poses a risk to your household’s health, besides damaging your AC. It’s another reason why this problem has to be addressed right away. Besides, the noise alone is intolerable.

You also need to turn off your AC when it whistles loudly at a high pitch because inside your compressor, there may be high internal pressure. This is actually quite dangerous, which is why you need to turn off the AC right away. Some of the more advanced AC units have sensors to detect this potentially dangerous situation, and they may do an automatic shut down when the sensors detect the problem.


It’s best if you have regular checkups for your AC. These can prevent problems, and the noises that go with them, from having to become issues in the first place. Do your owner’s maintenance tasks as well, such as replacing the filters regularly.

Just remember, if your AC starts to make a noise, it means that something’s wrong. Ignoring the problem won’t make it go away—it’s more likely to get more serious and more expensive to fix later on. So have it fixed ASAP!

Or, stay proactive and save a whole bunch of money for the day your A/C needs repair and get protected by an Armor Home Warranty today!

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