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Hearing AC making strange noisesYour air conditioner is probably one of the most used and important parts of your home. It’s responsible for keeping your house cool and comfortable. When an air conditioner is working properly, it often goes unnoticed. But once it starts making strange noises, you likely start to notice it and wonder what needs to be fixed. When it comes to heating and cooling in Longmont, it helps to know what causes strange sounds. Here are seven noises AC units might make and what they could mean.

Squealing Sound

A high-pitched squealing sound from your air conditioner can be unsettling. In many cases, the sound comes when the belt that connects to the motor slips. If this is the case, you’ll hear the sound both inside and outside your home and the belt needs to be replaced. Most newer air conditioners don’t have motor belts, so you’re more likely to hear this sound in an older system. If you hear squealing in a newer unit, it could be an issue with the bearings on the condenser fan motor, which could signal that you need a new motor.

Banging Sound

If a piece of the air conditioner is missing, it can cause a banging sound in the unit. In many cases, banging comes from a loose rod or piston pin in the condenser. To fix the strange noise, replace the loose or missing part.


Humming Sound

Many air conditioners make a low humming sound when they run, which is usually normal. However, if the humming sound is louder than usual or uneven, it could signal an issue with the AC unit. Loose parts or piping can lead to vibration and humming. This typically isn’t a very serious issue, but it can lead to larger problems if it isn’t addressed.

Hissing Sound

The most likely reason for a loud hissing sound is a refrigerant leak. Refrigerant is the liquid that cools the air and is one of the most important parts of the entire system. A hissing sound is often accompanied by an air conditioner that isn’t working efficiently or cooling the air. Refrigerant leaks are likely due to skipping routine maintenance and should only be fixed by an HVAC professional.

Rattling Sound

The more an air conditioner runs, the looser its parts naturally get. A rattling sound likely signals that the pieces are wearing down and getting looser. Rattling often happens when the fan gets loose. Another possible scenario is that there is debris in the AC unit, such as old leaves or twigs. An HVAC technician can perform an inspection and tighten the pieces and clean the machine to stop the rattling.

Buzzing Sound

A buzzing sound can come from a number of areas in an air conditioner, but it likely means the same thing: something is loose or missing. If a piece gets loose or falls off, it causes the other parts of the air conditioner to work harder, which can put things into overdrive and lead to a buzzing sound. Because a buzzing sound can be from so many different things, your best course of action is to call an HVAC technician for an inspection of the entire system.

Whistling Sound

A loud whistling sound could signal an issue with the ductwork. Air escaping the system or going to places it shouldn’t can often create a whistling noise. Whistling is more likely to occur in air conditioners that have dirty filters or old ductwork. Houses that have replaced parts of their ductwork over time could also be more prone to a whistling AC unit if the pieces aren’t connected properly.

If your air conditioner is making a funny noise, don’t just sit back and wait for it to fix itself. Take proactive steps to call a professional to look at the unit before that strange sound leads to a larger problem.