air conditioning

Why Your HVAC System Is Making That Noise

If you notice your air conditioner making strange noises, it could indicate something is wrong with the system and needs to be fixed. Some common causes of strange noises from air conditioners include loose parts, debris in the system, or worn-out parts. If you’re unsure what’s causing the noise, it’s best to contact a professional for help.

1. Humming

The humming noise coming from your HVAC unit can signify that there are loose or damaged components in the unit, specifically the condenser fan motor or the contactor relay switch. If the condenser fan motor cannot spin properly, it will create a humming noise. The contactor relay switch is responsible for starting the outside condenser unit. It will produce a humming sound if it isn’t working correctly due to an electrical or mechanical failure.

2. Loud Banging

The banging noise you’re hearing from your HVAC system may be coming from the compressor or blower fan. If the noise comes from the outside unit, it could be caused by a broken or loose rod, fan blade, piston, or another component.

3. Buzzing

If you start hearing a loud buzzing noise coming from your HVAC system, you should turn it off and have it checked by a professional as soon as possible. The noise could be a serious issue, such as a loose fan motor, a faulty air filter, loose or unbalanced fan blades in the outside condenser unit, dirty condenser coils, an obstruction in your copper lines, or a refrigerant leak, debris, or loose components.

4. Screeching

You may occasionally hear a screeching or metal-on-metal noise from your HVAC unit. If the noise is coming from inside the unit, it may be due to a worn blower belt or a faulty blower motor bearing. The noise coming from the exterior unit may be due to a broken fan motor or compressor.

5. Clicking

If your HVAC unit is making clicking noises, it could be a sign of a serious problem. The capacitor helps to start the motor and keep it running, so a broken capacitor can cause the motor to fail. The electrical connections can also become loose and cause clicking sounds. If your HVAC unit is making clicking noises, you should have it checked out by a professional to make sure there are no major problems.

6. Hissing

There is a leak in the air duct of the HVAC unit, which is causing a hissing sound. This air leak could be due to an improperly installed air filter or a filter that is the wrong size for your unit. Other possible causes of the hissing sound include a broken valve, a leak in the refrigerant line, or high compressor pressure. Whatever the cause, it is important to address the problem as soon as possible, as it can impact the operation and efficiency of the HVAC system.

7. Bubbling

If you hear a bubbling or gurgling sound coming from your HVAC unit, it could be a sign of a problem with the refrigerant or drainage line. This can happen if the drainage pipe is blocked, broken, or has holes in it.


There are many reasons your HVAC system might be making noise. It could be due to the fan, the compressor, or loose parts. If you’re not sure what the source of the noise is, you can always call a professional to take a look. In most cases, the noise can be fixed relatively easily.

AutumnAir is a family-owned HVAC repair service in Pelham, AL. We provide heating, ventilation, and air conditioning services to both residential and commercial places, ensuring that our clients stay comfortable and safe in the middle of an Alabama heatwave. 

We’ll guarantee your AC keeps functioning the way it’s meant to. Let us take care of your AC needs, from simple maintenance to complex repairs and total replacement. Get in touch with us and let us know how we can help!

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2010 Old Montgomery Highway
Birmingham, AL 35244

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