When your home cooling system works as it should, you will hear little more than the air movement through the ducts and out of the vents. Loud noises should never be ignored, as they can signify potentially serious operational issues that require air conditioning repairs. Here are three of the more common AC noises and what they mean.
Squeals can have a few possible causes, the most common of which is a loose belt. A worn or misaligned fan belt will naturally loosen and emit a squealing sound. This noise could also mean a failing fan motor, blower motor, or blower wheel. Bear in mind that some ACs do squeal slightly when you start them, so if this is a sound your system has always made briefly upon startup, then it's probably not a serious problem. But if the squealing is new, have an air conditioning repair professional check out the system.
If you hear banging coming from the AC's outdoor condenser unit, the cause is most likely a loose compressor part, like a connecting rod, crankshaft, piston pin, screw, or spring. If the sound comes from the indoor portion of your AC, it could also indicate a loose part or an unbalanced blower motor. To prevent more severe internal damage to the system, shut off the unit and schedule prompt air conditioning repairs.
Buzzing or humming sounds also have several potential causes, including loose parts, a dirty or clogged air filter, and an unbalanced blower or fan blades. There's a chance the source could be a refrigerant leak, depending on its location and severity.
A more easily fixable cause of buzzing or humming occurs when the rubber feet on the bottom of the AC start to deteriorate, compromising the unit's stability. Given this sound's wide range of possible causes, it's best to shut down the unit and plan for repairs as soon as possible.