Diagnose and Fix Various Air Conditioner Noises

Modern air conditioners come with new technologies that make them run quieter than ever. High-efficiency ac units feature sound-dampening technology and a two-stage (adjustable speed) compressor so that the noise level doesn’t go over 55 decibels.

All in all, your air conditioner should run quietly, and any weird noises coming from the air conditioner throughout regular operation are alarming. Never postpone addressing the air conditioner if you notice strange noises, as they may signal that repair or replacement is necessary.

When you don’t take care of the weird noises coming from the air conditioner, the minor problems can become significant issues. The sooner you identify the cause of the sound and solve the ac problems, the lower the problem’s chance to aggravate.

Some of the ac sounds are still normal, and you shouldn’t stress about them. At the same time, an air conditioner making noise when off is always something to worry about.  Distinct and specific noises are expected when the ac starts running and even stopping at the end of its cycle. It’s the humming, hissing, pulsating, and anything similar that you should worry about. Accurately identifying the sounds of the ac is essential for discovering the root of the problem. Pay attention and use your ears next time you hear some weird noises coming from the ac.

We’ve listed down the most common strange noises coming from your ac. It’s a place to start diagnosing the ac.

1. Air conditioner making pulsating noise

Some pulsating from the air conditioner is normal, but if the sound is loud and you can hear it from a distance, it’s time to worry. The sound could inform about a part of the panel is loose. Some components, such as the coil fan or the motor’s fan blade, could be loose, causing the sound.

In some situations, the pulsating sound may come from the fan motor, signaling that it needs to be replaced.

All in all, the pulsating sound isn’t as serious as squealing or banging noises coming from the condenser. It’s not a bad idea to call the HVAC technician to come and check the ac anyway.

2. Air conditioner making a gurgling noise

Sometimes, you hear a gurgling/bubbling sound while your ac is running. It’s not always straightforward to say where the sound is coming from.

Common causes for the gurgling sound are a condensate drain line gurgling or a refrigerant leak on the ac. You don’t have to stop running the ac. However, you should ensure that the condensate drain line has the correct trap.

If the refrigerant is the possible cause, you should call the HVAC professional for further investigations.

3. AC making a banging noise

Nine times out of ten, the banging noise signifies that a part is loose or even broken. A piston pin, a connecting rod, or even a crankshaft inside the ac compressor could be loose or damaged, causing the sound. Sometimes, something simple like an unbalanced indoor blower could create a banging sound.

When the system requires a new compressor, the banging sound may also occur.

4. Air conditioner making a hissing noise

Your ac may generate a hissing noise or a screaming noise. The noise typically occurs outside the ac unit as you turn on the unit, lasting 10-15 seconds before it stops. Unfortunately, your ac unit could also turn off and turn back on repeatedly.

The compressor is the cause of the sound most often. High pressure may build up inside the system, which makes the compressor create screaming/hissing noises.

It goes without saying that you shouldn’t run the ac anymore, as high-pressure building up is very dangerous. Turn off the ac right away and call the professional for repairs. A reliable ac unit should come with a safety switch that turns out the air conditioner when the pressure is too high. However, even the safety switch could be malfunctioning, so make sure you manually turn off the ac unit.

5. Air conditioner making a clanking noise

Clanking is yet another sound generated by loose/out-of-balance parts. The components inside the sealed ac unit may have failed, or the compressor may have become loose. More often than not, you will need to replace the compressor.

A clanking sound may also occur when the outdoor fan, indoor blower, or the fan’s blades aren’t balanced anymore. They hit other components and cause noise.

Even if the clanking noise isn’t signaling severe problems, it does signal problems that need fixing to not aggravate in time.

6. Air conditioner making a clicking noise

Electrical components of the ac will create clicking noises at start-up and shutdown, so it’s normal to hear them.

However, if the clicking is constant and doesn’t stop, you should see what’s wrong. A defective control or a failing thermostat could cause the clicking sound. The ac unit is made with many electrical elements, making time to check the possible electrical problems before it all gets worse.

7. Air conditioner making a loud buzzing noise

Several problems could cause the loud buzzing sound on your ac, and each of these problems requires some fixing.

Loose parts in the unit, or debris in the outdoor or indoor unit, but a loose outdoor fan motor or ready to fail motor could generate the buzzing sound. The buzzing noise may also occur when the fan blades are improperly balanced or loose or when the copper lines from the outside to inside rub against something.

An air filter that requires replacement and a condenser coil that needs cleaning will also generate a buzzing noise. Should the ac unit’s blower be unbalanced or has gone wrong, you will notice the disturbing buzzing noise.

Last but not least, the refrigerant may be leaking, so you don’t deal just with the buzzing noise but also with an ac unable to freeze up. If your ac unit doesn’t cool, the refrigerant leaks could be the reason, and the buzzing sound is just helping you identify the cause.

8. Air conditioner making a squealing noise

It’s typically the fan and blower that make the squealing, rattling noise that travels through the duct system. Indoor blower motor and outdoor fan motor also make powerful squealing sounds if they’ve gone wrong.

In case of malfunctioning, the blower wheel and housing will also create a squeal. Keep in mind that the squealing sound is typical for some units upon start-up. Therefore, please pay attention to the unit whenever it is making the sound. It’s not always signaling a problem.

9. Air conditioner making a humming noise

Even if the humming sound isn’t always something to worry about, it can still inform that something inside the air conditioner isn’t running correctly. Refrigerant piping or some loose parts may generate vibration that may cause more severe problems when left unaddressed.

Humming or buzzing sounds coming from the ac unit may also signal electrical issues. When the compressor hums and doesn’t start, a problem on the motor or some loose wiring may generate the humming noise.

10. Air conditioner chattering/rattling

When the ac creates a rattling sound, it means that the air conditioner begins to deteriorate, and some of its components already loosen. Leaves or twigs can also clog the system, causing the chattering sound.

It’s also possible that the electrical contractor in the ac unit generates the chattering noise. It would help if you didn’t postpone fixing, as other components, the compressor included may get damaged.

The fan could also rattle if it is loose, so check it too. Loose screws or bolts in the clean condenser coils, the unit’s casing could be loose and cause the sound.

11. Air conditioner making a screaming noise

Should screaming o high-pitched whistling noises come from the ac unit, you should turn off the ac unit right away and call the HVAC technician. A refrigerant is most likely the cause, and the problem damages the unit and poses a threat to your health.

High internal pressure may also cause a screaming sound, and it’s a dangerous situation. Don’t worry if the ac shuts off automatically. It’s a safety feature, and the sensor is doing the job of keeping you safe, turning off the ac unit.


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