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Why Is My Air Conditioner Making a Humming Noise?

Air Conditioner On Wall Background

Are you worried about the humming noise in your air conditioning unit? Air conditioners are ideal for cooling the house and improving air quality around the home or office. However, any noise made by your AC system can be an indication of a problem.

On the bright side, humming sounds should not keep you up at night as long as they are dealt with swiftly. There are a couple of reasons why your HVAC unit is humming.

We will identify the culprit and find suitable solutions to the problem.


Though low humming is expected in your air conditioner, loud humming noises are caused by vibrating refrigerant pipes, a faulty condenser fan, or a frozen AC unit.

A defective contactor relay switch, circuit breaker, or damaged wiring can also cause humming and buzzing in the appliance.

If you notice any other strange noises from your aircon unit, you should call an expert to look at the system. It might indicate a severe issue that needs fixing.

7 Reasons Why Your Air Conditioner Is Humming

A slight humming sound is expected when dealing with an AC system. The condenser’s blade motor makes a humming noise as it pushes air to cool the refrigerant.

However, if you hear an unfamiliar hum in your central air conditioning unit, you might have another issue with the appliance.

Here are some of the culprits:


Large aircon systems are prone to making noises like hissing, rattling, humming, or buzzing. However, if the noises get louder and more persistent, it is crucial to call a repair professional to identify the problem.

1. Vibrating Refrigerant Pipes

A Connection Of Ac Copper Pipe That Connects The Ac Compressor

Another common reason for the humming in your AC unit might be unsecured pipes. Vibrations are typical as the system runs and refrigerant gets pushed through the conditioner.

In addition, an improperly mounted expansion valve can also cause the refrigerant pipes to vibrate, which sounds like humming.

Refrigerant leaks can be a massive hazard to your health and your property. An expert HVAC technician should be called to fix any vibrating pipes to avoid damaging the refrigerant tubes.

In addition, if your refrigerant line is unprotected, you should ask the technician to cover it up with a protective enclosure for extra precaution.

2. Faulty Condenser Fan

Grey Outdoor Ac Condenser Unit

The air conditioner might have a defective condenser fan if you notice loud humming. As we previously stated, the fan is responsible for most of the humming from your unit.

However, a defective fan experiences more resistance when spinning, leading to louder noises. A clogged fan or fan motor can also produce loud humming.

Climate control units with a failed condenser fan also have difficulty regulating room temperature.

You might notice that the system has irregular cooling cycles or require more time to reach the intended temperature.

Replacing an AC condenser motor is not your typical DIY project. Without technical expertise, you risk damaging the unit.

You should contact your local HVAC repair technician to help with the installation.

3. Electrical Malfunction in Contactor Relay Switch

White Square Light Switch Combined With A Ac Power Socket

A faulty contactor relay switch might also be the culprit for the loud humming in your air conditioner.

The relay switch turns on the outside unit after the room’s temperature rises and the room needs to be cooled. It provides power to the compressor and condenser fan and turns the aircon on and off.

Over time, the contactor switch can fail due to wear. When this happens, the relay switch cannot turn off the condenser even though the thermostat is off.

After the contactor switch malfunctions, it often produces a humming sound. Though the contactor relay switch is easy to replace, a high-voltage current often runs through it.

We recommend hiring a qualified professional to handle it.

4. Overloaded Circuit Breaker

Turning On Circuit Breaker On Control Panel After It Has Tripped Due To Overload

In addition, you might also notice a humming sound if your circuit breaker is faulty. The circuit breaker controls the current flow to your climate control unit. In case of an overload, the breaker trips, preventing damage to the AC.

However, if you have a faulty circuit breaker, overloading can cause vibrations in the wiring, often heard as an electrical humming.

Like the contactor relay switch, there is an electrocution hazard when dealing with a faulty circuit breaker.

Unless you have the technical skills, you should call an electrician to look at the issue.

5. Wiring Issues

Hand Stitches Power Connection On Electrical Panel

Naked, damaged, or loose wire connections can cause a humming, buzzing, or sparking noise.

Current can often jump from one wire to another, causing arc faulting. In addition, damaged cables also have a high risk of leaking current.

Loose or naked wires should be dealt with immediately. Always call a professional to insulate wires or secure loose connections.

6. Air Conditioner Freezing Up

The Outdoor Unit Of The Air Conditioner Is Covered With Ice And Icicles

Frozen air conditioners can cause loud buzzing or humming noises. When the ice starts forming around the blower, condenser, or evaporator coil, the climate control unit must work harder to ensure proper cooling and air circulation, causing the loud humming.

There are multiple reasons why your cooling unit might be freezing. Before fixing the issue, you need to deal with its cause.

7. Loose Components in AC

Air Conditioner Capacitor

Likewise, loose components in the HVAC might also be causing the humming. Over time, wear and tear can break parts of the air conditioning unit, causing them to get dislodged inside the appliance. The loose parts can vibrate as the system runs, causing the humming.

The best option is to get a qualified professional to identify which parts are dislodged and do the necessary repairs.


Though slight humming is expected when dealing with massive AC units, when the sounds get louder and more consistent, it might be an indication of trouble brewing.

Vibrating refrigerant pipes, a clogged or defective condenser fan, or lose components in the AC are common reasons for the humming.

Faulty wiring and circuit breakers can also lead to arc faulting that causes buzzing and humming. Lastly, a frozen AC can also be an issue.

Regular maintenance can help identify potential issues with the air conditioner and fix it beforehand.

Repairing an Air Conditioner

Air conditioners are delicate appliances that require expert skills when fixing. To avoid further damage to the unit, you should always call an HVAC repair expert to help.

Additionally, you should always use genuine manufacturer-recommended parts during repair to prevent compatibility issues and improve your unit’s efficiency.

Frequently Asked Questions

Is It Normal for an AC To Hum?

Low humming in your air conditioner is completely normal. However, if the unit starts loud humming or buzzing, you should call a repair technician to look at it.

What Is the Lifespan of an Air Conditioner?

An air conditioner can last for 16 to 20 years with proper maintenance.

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