5 HVAC Sounds You Don’t Want To Hear

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No matter its age, your air conditioning and heating system can sometimes display issues. Some occasional sounds from your HVAC unit are completely normal — it means the system is working as it should. However, unusual sounds are cause for concern, and homeowners should call in the professionals as soon as they hear the following strange noises coming from their unit. Letting these issues continue can lead to bigger, more expensive problems down the road.

The HVAC repair specialists at Bloomington Heating and Air can help when you need AC repairs. Our HVAC company is known for delivering quick, effective HVAC services that homeowners need.

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Thumping, Clanking & Clanging 

Thumping, clanking, or clanging sounds usually indicate a problem with the blower assembly or motor. Rattling usually means a component in the system is coming loose. The problem should be repaired by HVAC technicians before the part breaks or disconnects completely. If you hear louder banging sounds when the blower is running, shut your AC system off. 

Repeated Clicking 

Clicking noises are completely normal when your HVAC unit turns on and off. If you hear repeated clicking sounds coming from the control panel or outside compressor, a relay might be defective. An electrical control may also be causing the relay to timeout and fail. If you hear these sounds, contact us right away to prevent bigger problems in the future. 


If you hear a fast “thwapping” sound when the blower is running, something may be stuck in the blower blades, or there might be something inside the housing that is contacting the blower while it turns. While “thwapping” may not be critical, if an object or debris creates resistance, the motor may wear out abnormally fast, leading to greater issues down the line.

Squealing Or Screeching 

Squealing noises from the blower motor can indicate a bad belt or motor bearing problems. Belts are generally not an expensive repair. They should be replaced before they break; if they do break, your blower will no longer turn. Many blower motor units have oil ports for adding lubricant, while others are sealed.


When the fan turns on in your compressor unit, it should not rattle. These sounds may be an indication of loose hardware or a failing motor. The louder the sound, the more serious the problem can be. If the noise is similar to a scream, your compressor may be failing. Contact our HVAC professionals immediately for repairs if you hear this sound.

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