Air Conditioner Noises To Be Aware Of

image of homeowner trying to sleep but can't due to air conditioning noises

No air conditioning unit is completely quiet. Even new units will produce certain sounds which are completely normal for day-to-day use. Most of the time, these noises are the result of normal operation and nothing to worry about. In some cases, however, the air conditioner making noise may be a symptom of a bigger problem and should be inspected by a professional HVAC contractor right away. Noises are usually a sign that a component or components are not working as they should. Consequently, the air conditioning unit may not be functioning as it should.

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What Air Conditioner Noises Should I Watch Out For?

Modern air conditioners are much quieter than older models. Thanks to HVAC technology, many models include noise-dampening technology with variable speed compressors to ensure AC units generate noise at just 55 dB or less. This is the level of noise that a normal dishwasher produces. If the AC unit has a problem, it is likely that it will produce any of these sounds:

AC Unit Is Buzzing

Buzzing AC noises may point to an electrical issue or fan blades in the outdoor condenser unit that is loose or out of balance. The buzzing noises may also be caused by other loose components, dirty condenser coils, or a damaged outdoor fan motor. If your AC unit has a refrigerant leak, it will usually produce a distinct buzzing noise.

Humming Coming From A/C System

image of an air conditioner compressor

A humming air conditioner noise may be a sign that its contactor relay switch is defective. If this component is damaged, the AC may fail to turn on. The thermostat sends a signal to the contactor relay switch to start the outdoor unit or condenser. This type of issue is an electrical problem and should only be handled by a licensed HVAC technician. In some cases, humming noises are caused by problems with the fan motor.

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Air Conditioner Clicking

Clicking noises can be confusing because they may sound similar to the noise that the AC makes when a cooling cycle starts or ends. However, if the clicking sound is frequent or continuous, there might be a problem with the thermostat. If this is the case, the thermostat may have to be replaced. Make sure this is performed only by a licensed cooling technician.

Air Conditioning Screeching Sound

image of an outdoor air conditioning unit

One of the most distinct noises that a defective AC unit produces is a screeching sound. The most likely culprit for this is an issue with the condenser unit’s fan motor, which is likely malfunctioning. The primary role of this fan is to eliminate heat from the coolant or refrigerant. If the fan is damaged, the AC will fail to lower indoor temperatures.

Screeching noises may also be traced to a blower fan motor that has been damaged. Blower fans help remove heat and humidity indoors, pushing the air to the return ducts from which it is cooled by the AC system. The blower fan then distributes the cool air throughout the house via the air vents.

Other possible reasons why the AC unit is producing screeching noises are damaged fan motor bearings and a bad fan belt. If your AC unit is producing a loud screeching or squealing noise, call your HVAC contractor right away.

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Air Conditioner Clanking

If the AC system sounds as if a metal part has gotten loose and is hitting another metal part, you likely require a parts replacement.  Unbalanced or loose parts can lead to clanking noises. If the blades of the outdoor fan or indoor blower have come loose or are not balanced, they will hit other components. This in turn produces the clanking sound. If this is the issue with the AC, do not hesitate and call an HVAC technician immediately. Do not wait for the problem to worsen. Keep in mind that metal hitting metal can only lead to further damage and costly air conditioner repairs.

A/C Unit Whistling

ac refrigerant leak

A whistling or a high-pitched noise that sounds like the AC is screaming is another symptom you need to watch out for. The noise is usually a refrigerant leak or high pressure within the compressor. Either issue is serious and only a professional should handle it right away. If this happens, turn off the unit and call your local HVAC technician.

Cooling System Is Banging

Banging noises can often be caused by a defective compressor. These sounds are fairly common in older air conditioning systems. With age and regular wear-and-tear, the components of the AC unit may become loose or unfastened. It is also possible that a part of the AC unit is broken. The likely components include the piston pin, crankshaft, or connecting rod, which are located inside the compressor. An imbalance indoor blower may also lead to banging. If this problem is present, you likely will need to have an air conditioner compressor replacement.

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Whirring Air Conditioning Unit

If the AC sounds as if it has a drone within it or worse, a helicopter, you may be dealing with a mechanical issue such as a faulty fan, a malfunctioning fan belt, or a damaged blower fan motor. A loose fan blade produces a whirring sound. In a best-case scenario, the problem may only be trapped debris in the outdoor fan unit or indoor blower fan. If you are familiar with how a piece of paper sounds when a fan hits it, that is the sound you should consider a warning.

Rattling Coming From Air Conditioner

Loose debris inside the outdoor condenser unit can lead to a rattling noise within the air conditioner. These may include dirt, leaves, or twigs that have fallen into the unit. This is an easy fix – simply open the outdoor unit and remove the debris. If the unit is otherwise clean, the noises may be caused by a problem with the AC electrical contractor. Get this fixed right away to prevent more serious damage.



Air conditioners that have passed the manufacturer’s quality test and were installed properly should last you a good 15 years or more with regular air conditioner maintenance and reasonable use. However, time does catch up with the unit and it may no longer perform in the same way it used to. If you are unsure about what to do, never assume that the problem is simple. Get in touch with your trusted HVAC contractor so they can identify the problem correctly and apply the correct solutions.

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McAllister Energy

McAllister Energy offers high-quality HVAC services in Camden County, New Jersey. We hire only the best professionally certified technicians who conduct superior heating and cooling services. Some of our HVAC services include indoor air quality solutions, HVAC maintenance, heating and cooling installations, repairs, ductless systems, and much more. All our techs provide accurate HVAC services on time, every time.

Our company guarantees affordable heating and cooling service rates. Our maintenance services can increase your home’s comfort, energy efficiency, and cost-effectiveness. We can also provide you with a highly energy-efficient HVAC replacement system that fits your budget. Your satisfaction is important to us, so all our work comes with a guarantee. Book a service appointment with McAllister Energy today. We provide free, in-home estimates.

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