What are those strange noises my central air conditioner
is making?

Central air conditioners have many moving parts that must work together to keep your home cool. There are fans, hoses, belts, compressor motors, coils and other components that work together to move cool air throughout your home. As air conditioners age, the belts often become loose, leading to thumping sounds. A clogged air filter reduces air flow and can cause the unit to whine as it cycles on or off. Loose hardware on compressor parts can lead to rattling sounds.

RATTLING NOISES
Rattling noises are pretty common with air conditioners. Over time, the various fasteners attaching components to the unit can come loose. If you hear rattling, check the screws or bolts holding the cover plates in place. If the rattling noises persist after tightening the panels, remove the cover and check internally  for the same issue. After listening for rattles, always turn the power to the unit OFF at the breaker.

WHISTLING SOUNDS
Whistling sounds are usually hear when seals are leaking. Check for cracks and gaps in the seams of ducts near the unit and the duct work that carries the air throughout the home. Examine the seams around these areas for loose connections and re-tighen any screws or bolts. If heat tape was used to also cover the seals, make sure the taple completely adheres to the duct seams.
SCREECHING SOUNDS
Like your car, the air conditioner motor uses belts. If there is a periodic screeching that only occurs when the unit turns on to blow air or cool the air down, it is likely a worn-out belt that needs to be replaced. Over time belts can stretch and wear out. A qualified HVAC technician should check the belt and replace it if needed.

CLUNKING SOUNDS
Clunking sounds can mean something has come loose inside the air conditioner unit. A loose fan blade on a motor can make sounds as it turns. Or it could be a plastic component or cover plate coming into contact with the blade. A qualified HVAC technician should inspect the unit to ensure it is operating safely.

Most new air conditioners built within the last 5 years are designed to operate very quietly. When you hear unusual noises, it is usually the result of a lack of maintenance or a sign that a part has worn out and is about to fail. By being aware of these noises you can address the small problems before they lead to a breakdown.