The answer to 'preventive maintenance making noise' is that common causes include worn bearings, loose components, or issues with the blower motor or fan. Symptoms may include rattling, squeaking, or grinding noises. Solutions can range from tightening loose parts to replacing worn components.
In many cases, minor noises can be addressed through basic DIY maintenance. However, if the noise is persistent, getting louder, or accompanied by other issues like reduced airflow, it's best to call in a professional HVAC technician. They can properly diagnose the cause and make any necessary repairs to restore quiet, efficient operation.