If your system is making some strange noises, it could be a sign that your system is failing. When your unit is functioning normally, it is usually fairly quiet. Certain noises can definitely warn you that your system needs some attention.
Loud thumping, clanking, rattling, or banging noise
Generally, these sounds could indicate a problem with the blower or the motor. It is possible that something in the system is coming loose. If you hear a loud banging, more than likely something has broken or became disconnected. It is best to turn the system off and call a professional to have your system looked at.
Repeated clicking noise
Clicking noises are normal when your system is being turned off or on, but if you hear repeated clicking sounds coming from your control panel or outside compressor, it’s a good idea to get it looked at, it is possible a relay could be bad.
Loud squealing noise
Squealing noises can indicate a bad belt or motor bearing issues. Belts are usually an inexpensive fix and should be replaced before they break to prevent further damage. Motor blower units sometimes have oil ports that will need lubricated.
Rattling or screaming noise from the compressor and fan unit
Your fan in the compressor unit should not rattle. If it does it could indicate that something is loose or that your motor is failing. If the noise is similar to a scream it may indicate that your compressor is failing.
As you can see there are many noises your HVAC System can make, and many reasons behind them. Regardless of the age of your system, it is possible that you can encounter problems. It is always best to call a professional whenever you start to hear an unusual sound, just to be safe.