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8 HVAC Noises You Shouldn't Dismiss Until You Call a Technician


Older model HVAC units are naturally noisier than the more modern versions. However, there are still some noises from your air conditioning system that you should never ignore. Some of them can be signs of minor problems that can grow into more costly issues if left unaddressed. Neglecting these early signs of an impending problem can result in bigger issues, costly repairs, and even replacement.

Here are eight sounds that should prompt you to call your service technicians to have your unit checked.


This sound is typically an indication that there is a loose or broken part within the unit. The blades of the outdoor fan or the indoor blower may be out of balance, causing them to hit against other parts. It may also be a sign of a loose compressor or a failure in some parts of the sealed unit. Loose or broken elements can create more damage within the unit.


A buzzing noise may mean several things, including debris in either the indoor or outdoor unit, loose parts, loose outdoor fan and out of balance fan blades. A buzzing noise can also mean that it is time to clean your condenser or change the air filter. Other possible causes of the sound are leaking refrigerant and a destroyed blower.


Humming can signal a loose part in the air conditioner or refrigerant piping, or a loose wire. If left unchecked, it can lead to more costly maintenance problems over the life of the unit. If a humming compressor makes a loud sound and also cannot start, your motor may be having an issue.

Rattling and Banging

The sounds of rattling and banging are common when the motor or blower assembly inside your HVAC unit has a problem. Loud banging shows that a component is coming loose, has been disconnected or is broken. Rattling may also be due to a misaligned blower, even though motor bearings too can cause the sound. In case it is the motor, a qualified technician should attend to it immediately to avoid the motor burning out.


Bad belts or problems with motor bearings can cause squealing noises to come from within the blower. It is wise to replace the belt before a crack or breakage occurs, because once they do your blower will not turn. If this happens in the middle of the night, it can result in discomfort for your family as you wait for a repair technician to help.


A distinct and different sound from squealing, screeching is the result of a dry blower motor. The motors with a HVAC unit need oiling regularly to allow the unit to function. Some of the units have oil ports for lubrication, which a technician will use to apply the proper oil to keep the system lubricated.


A high pitched whistling, which is sometimes called screaming, from your air conditioner is a critical signal. It mostly results from a leaking refrigerant. You should shut down the HVAC and call a technician immediately. The problem can not only destroy the air conditioner, but is also a threat to the health of your family. It also indicates a high internal pressure, which is not a good thing.  This situation can become hazardous if the sensor does not shut down the blower in time.

Clicking sounds

Clicking is the sound produced when the HVAC is turned off and on. A repeated clicking indicates a faulty contactor. Failures in the electrical control or a wrong connection might be causing the relay to time-out continuously.

In case you notice any other unsettling sound from your HVAC, the first precaution you should take is to turn off the system and call an experienced professional for help. The qualified technicians of David Gray HVAC can assist you at any time of day or night. Click here to get started.