Why My AC Unit Makes Loud Noise When Starting?

Why My AC Unit Makes Loud Noise When Starting?

Air conditioning units are made for home comfort and provide good quality of air and home environment. But if your air conditioning units are constantly making noises, it ruins everything. 

Modern air conditioners are designed with sound-dampening technology to minimize distraction created by noises. So if you ever find yourself constantly bugged out by noises made by your air conditioning unit, to help you out.

Here are some of the usual noises and their indications:


A high-pitched or hissing sound. If you ever encounter this noise, shut your air conditioning unit immediately, and call a professional right away. It is too dangerous for you to handle it. It could be a sign of high internal pressure within the compressor. It could also be a sign of a refrigerant leak, which not only damages your unit but also threatens you and your family’s health. If your unit turns off on its own, don’t panic. It is because your sensor is detecting some hazard and it is doing its job to save you from it.


When you hear this kind of noise, it is usually caused by deterioration and loosening of some parts. Another cause could be some debris like twigs and leaves that could be stuck inside. Another culprit could be the fan blades. When fan blades are loose, it could make some rattling sound. In some cases, it could be coming from loose electrical components. 

Squeals and Squeaks

These particular noises are usually coming from your blowers and fans that are transmitted through the duct system. Usually, outdoor fans are squealing and squeaking when they are becoming worse. In rare cases, the blower wheel and its housing may also be the cause of these noises. For some units, these noises are normal upon starting up. It’s up to you to identify whether the sound is something already there from the start or if it is something new.


This sound is usually normal upon start-up and shutdown, but constant ongoing clicking sound may be a sign for something serious. It might be a sign of a defective thermostat or a failing control system. It could also be caused by several electrical components inside your unit. It’s best to monitor and pay attention to this noise to save you from something worse in the future.


Clanking is usually a sign that there are some unbalanced or loose parts inside the unit. The parts inside the unit may have failed, or the compressor might have become loose, which may need to be replaced in no time. This could also indicate that the fan blades inside are loosely-attached, causing it to hit other parts. 


Usually, banging is a sure sign that some parts are loosely-connected or broken. The culprit could be the connecting rod, the piston pin, or the crankshaft, all of them being inside the unit’s compressor. In some cases, it may also be caused by a loose or unbalanced indoor blower. In the worst cases, it might indicate that your compressor needs to be replaced.

If you hear something unusual coming from your air conditioner, make sure to pay attention to it and address the problem by calling repair services. It is always the best decision to solve the problem right away. Not only it will save you money in the long run, but it also saves you from the hazards the noise may bring.