Outdoor AC Unit Making Noises? Here’s What They Mean

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Outdoor AC Unit Making Noises? Here’s What They Mean

AC Condenser unit outside a home

If you’re hearing unfamiliar noises coming from your outdoor air conditioning unit, don’t panic. Although it’s best to seek advice to address any unique issues with your AC unit, knowing what issues certain sounds indicate is a good first step toward repairing your system.

We’ve compiled a list of some of the most common noises outdoor air conditioning units make and what they typically mean.


If you hear a constant buzzing noise, especially when your AC unit is off, this is a clear indication of an electrical malfunction. Typical causes of a buzzing sound from your unit include loose electrical connections, a faulty contactor relay switch, and a malfunctioning fan motor.

All of these are electrical issues that should be addressed by a certified HVAC technician.


If your outdoor unit makes a banging noise when it turns off or on, this is an indication that your compressors’ internal springs, which support the pump within your unit, are uneven, malfunctioning, or broken.

However, if this noise occurs while your fan is running and not just when it’s switched on or off, a piece of the fan is likely loose and therefore banging against the sides of the unit, creating a slamming or banging noise.


A whistling sound is caused by high air pressure within your AC unit and usually is accompanied by a decrease in airflow coming from your vents.

An HVAC unit functions by attracting warm indoor air and cooling it by running it over evaporator coils. When this airflow is restricted, the air pressure inside the unit increases, resulting in the whistling noise.

Turn to Neffsville Heating & Cooling for AC Repairs

Whatever noise it is that your AC unit is making, call the qualified experts at Neffsville Plumbing, Heating, & Cooling to identify your problem and resolve it. We have kept Lancaster County homes cool and comfortable for over 80 years.

Contact us online or call (717) 625-1000 today for any of your plumbing, heating, and cooling needs.

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