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Pasadena A/C: 5 Air Conditioner Sounds Your System Should Never Make

Pasadena A/C: 5 Air Conditioner Sounds Your System Should Never Make

Pasadena A/CWhen it’s operating normally, your air conditioner makes certain sounds that you’ll become accustomed to hearing. If it starts making alarming or unusual noises, though, it’s often a warning that potentially serious problems are developing. If you can identify any of these air conditioner sounds, it’s time to call for professional help.

Rattling, Thumping or Clanking

If the sound is coming from the indoor air handler unit, a loose or misaligned blower assembly may be the cause. If you’re hearing this type of noise at the outdoor unit, it’s likely that a fan blade, motor mount or other hardware item has worked itself loose. Having the culprit identified and secured by your HVAC pro before it gets worse can prevent serious harm to adjacent components.


Hearing a brief squealing noise from the air conditioner at startup isn’t unusual, but an ongoing squealing sound can occur if the fan belt is worn or has slipped out of place. If the belt breaks, the blower fan will stop working, so have your HVAC technician address the issue promptly.

Bubbling or Gurgling

These distinctive sounds coming from the refrigerant lines or compressor indicate a refrigerant leak that should be located and repaired without delay to prevent a loss of cooling capacity and costly equipment damage.


If you’re hearing a buzzing noise but you can’t determine exactly where it’s coming from, it may be an electrical issue that poses a serious risk of fire. Possible causes can be a fault in the thermostat, electrical contacts, a compressor relay or circuit breaker that should be investigated immediately to ensure the A/C’s safe operation.

Hissing or Screaming

If you hear high pitched noises like these coming from the outdoor unit, shut down the air conditioner at the breaker and call for help right away. This type of noise typically points to a hazardous high pressure build up inside the unit that needs immediate attention.

If you’re hearing unsettling air conditioner sounds and need expert help, contact the pros at Air-Tro, Inc. We’ve served the home comfort needs of the Pasadena area since 1969.

Our goal is to help educate our customers in the greater Pasadena, California area about energy and home comfort issues (specific to HVAC systems).

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