Why Is My Air Conditioner Making A Buzzing Noise [7 Causes & Solutions]

When an air conditioner isn’t working properly, it can make a variety of noises. The noise can be used to pinpoint the source of issues. So what happens if your air conditioner is making a buzzing noise?

It is hard to give a single clear-cut answer to this question. Electrical arcing, loose parts, a frozen evaporator coil, a failed contactor, damaged isolation feet, or broken fan blades could all be to blame.

In the sections that follow, I’ll go over each cause of a buzzing noise in air conditioning units and show you how to fix it.

Common causes your AC is making a buzzing noise 

Even if I mentioned them at the start, if you are not tech-savvy, you may not know what they are. Let’s look at them one by one.

1. Electrical arcing

Air conditioners are powered by electricity. As a result of the numerous electrical components and wires inside, it is prone to electrical problems over time.

When an electrical component fails or a wire becomes worn, electricity can jump from one to another through the gas or air, resulting in an electrical arcing.

When it happens, your AC will produce a buzzing noise. 


Please do not leave it unattended because electrical arcing can cause burns, hearing loss, or even death.

You should turn off your AC immediately and make a call to a certified HVAC technician. They will detect the source of the problem and fix it.

Don’t try to solve it on your own because it is very dangerous.

2. Loose parts

Parts will become loose over time due to vibration created while in use.

Different noises can be produced depending on which part is loose. For example, some may result in a clicking noise, and some may cause a knocking noise

When these parts vibrate and rub against the surrounding parts, they may also produce a buzzing noise.

The loose parts can cause the components in AC to fail prematurely so that you should fix it as soon as possible.

What to do?

Unless you have prior experience preparing your AC and can pinpoint the source of the noise, you should contact a professional.

If you decide to do it yourself, take appropriate safety precautions, turn off the machine, and tighten the part with a screwdriver.

3. Broken fan blades

The fan blades on the condenser fan or blower can crack due to mechanical wear and tear or other factors. When the fan spins, friction occurs in the cracks, resulting in a loud buzzing noise.

What to do?

Power off your AC and ask a technician to replace the fan. 

4. Frozen evaporator coil

While leaky refrigerant in AC can make a hissing noise, it can also cause the evaporator coil to freeze. In addition, the debris the coil is caked with or the low outside temperature can also result in a frozen coil. 

When the coil is ice-coated, it makes a low buzzing or vibrating noise.

What to do?

Some air conditioners have a defrost mode that allows the coil to thaw before returning to work. If your machine lacks this feature, you can turn it off and let the ice melt naturally.

If your AC continuously ices up, you should contact the local contractor to detect related problems, such as any refrigerant leak.

5. Faulty contactor

faulty contactor

When a contactor fails, it can produce either a humming or a buzzing noise. Given that the contactor relay switch controls whether or not the electricity can flow through to the outdoor unit, the AC may not be able to turn on or turn off properly.

What to do?

The contactor needs a replacement. Fortunately, this component is pocket-friendly, ranging from $10 to $100. If you have the expertise, you can replace it. It is not a too complicated task. Again, please take safety precautions if you decide to do it yourself.

For those who don’t have the expertise, don’t take risks! An HVAC can remove and install the contactor for you, even though you need to pay extra money.

6. Defective isolator feet

ac isolator feet

The outdoor AC unit will make a vibrating or buzzing noise when operating. To remedy the noise, the isolator feet will be installed under the compressor or the outdoor unit, depending on which type of AC you have.

Because these feet are made of rubber, they will gradually degrade, losing their ability to reduce vibrating noise.

What to do?

The outdoor AC unit is pretty heavy, and the compressor is the heart part of your AC. Your best bet is to let a pro fix it. Remember to allow the ac to settle for 24 hours before turning it on if you can’t get the information in the instruction manual or from the technician. 

7. Damaged condensate pump

If the indoor air conditioning system is located in the basement, it is likely to have a condensate pump to properly drain the collected water.

It can become clogged or broken down, resulting in a buzzing noise. Even if the air conditioner is turned off, you will continue to hear the buzzing noise because the condensate needs time to drain.

What to do?

Condensate pumps are cheap and simple to replace. While hiring a technician is a good option, if you have repair experience, you can do it yourself. In any case, it’s not rocket science.

After turning off the entire system and unplugging the pump, you can begin disassembling the old one and installing the new one.

Can you use your AC if it is buzzing?

Generally speaking, you shouldn’t continue to use an AC that is buzzing because it can cause injuries, catch fire, or damage the whole system. 

If the buzzing noise is caused by a loose part and defective isolator feet, it may be able to continue to work for a while. However, it will lead to premature wear, which you also want to avoid. 

In a word, it is not recommended to use your AC under this condition.

How to keep your AC from making a buzzing noise?

Mechanical wear and tear can cause parts to become loose or worn out. Noises are common as your air conditioner ages.

Regular maintenance, on the other hand, allows the technician to detect the problem at an early stage. For example, if there is a crack in the isolation pad, they will tighten the parts before it starts buzzing.

In concluding 

There are many potential reasons for an air conditioner to make a buzzing noise. When the contactor, compressor, or fan fails, they can produce such a sound. The isolator feet could also be the culprit. 

You can use this article as a guide to trace the source of the buzzing sound. In most cases, contacting your local contractor is the best way to deal with it. 

About The Author

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Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested dozens of products in person, like humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.

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