Why Is My Central Air Conditioner Making a Squealing Noise Outside?

Written by steve smith
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Why Is My Central Air Conditioner Making a Squealing Noise Outside?
Central air conditioning units make a range of noises. (Comstock/Comstock/Getty Images)

An outside central air conditioner makes several loud noises due to the internal operation of the parts, pistons and compressor unit. All of these noises come from some kind of moving part or event inside the machine. Many noises like squealing sounds signal something else is going on inside the air conditioner.

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Typical Squealing Sounds From an AC

Just because the air conditioner is making a squealing sound does not mean the unit is damaged or malfunctioning. Most air conditioner units make a squealing sound when they begin to run. This squealing sound comes from the parts moving against one another inside the machinery. These parts scrape and squeal as they move. Gears, pistons and cogs in the blower motor and compressor all act like parts in a car engine. When they begin moving, screeching and squealing is bound to occur.

High-pitched Screams and Squeals

Higher pitched screaming sounds and squeals are another problem. These sounds are very loud and not your typical mechanical squealing sounds. They accompany a hissing sound and come from pressure inside the unit. This is a serious condition, and if you hear this sound from your outside central air conditioner, call a technician. Cut the power to the unit by turning off the breaker to the air conditioner. Leaving the system running may result in damage to the unit and loss of heating or cooling ability.

Lubrication Issues

Like any other machine, air conditioners need lubrication to run smoothly and quietly. Several parts on your air conditioner need lubricating oil, including the fan bearings and compressor. If there is low oil flow or no oil, bearings will grind and squeal and gears will screech, which translates into a squealing sound that is present during start-up and continues as the unit warms up and starts dispensing cool or hot air. A simple service call is all you need to fix this problem. Keeping up on your air conditioner maintenance is always recommended. Ask your technician to check and refill the oil if you hear continuous squealing coming from the unit.

Air Conditioner Noise Levels

Air conditioners maintain noise levels in the 8 to 9 bel range. "Bel" is a term derived from decibels, the measure of sound levels. A 9 bel system is very loud and considered 10 times as loud as the 8 bel system. If you have an advanced system that is under 7 bels, the squealing sounds may appear louder because your air conditioner has always run quieter. Consider this before you ascertain the seriousness of the squealing sound. The squealing noise must exceed the sound level of the air conditioner just to become audible.

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