The answer to 'HVAC system making noise' is that there are several common causes, including worn bearings, loose components, or issues with the blower motor or compressor. Symptoms may include grinding, squealing, or rattling noises that can indicate a problem.
In many cases, minor HVAC noises can be addressed with DIY maintenance like tightening loose parts or replacing worn components. However, if the noises persist or worsen, it's best to call in a professional HVAC technician to diagnose and repair the issue. Attempting complex repairs on your own can be dangerous and may lead to further damage to the system.