If you are hearing strange noises coming from your HVAC system, it is important to address the issue as soon as possible. The first step is to identify the source of the noise. If the noise is coming from the air handler, it could be caused by a loose or worn fan belt, a worn motor bearing, or a loose fan blade. If the noise is coming from the outdoor unit, it could be caused by a loose fan blade, a worn compressor bearing, or a loose or worn fan motor. Once the source of the noise has been identified, it is important to take the necessary steps to repair or replace the faulty component. If the noise persists, it is recommended to contact a qualified HVAC technician to inspect and diagnose the issue.