The answer to 'air handler making noise' is that there are several common causes, including worn bearings, a loose blower wheel, or a problem with the motor. Symptoms may include rattling, grinding, or high-pitched noises coming from the air handler unit. Solutions can range from simple DIY fixes to more complex professional repairs, depending on the root cause.
If the noise is mild and intermittent, it may just need some basic maintenance like lubricating the bearings or tightening loose parts. However, if the noise is loud, persistent, or accompanied by other issues like reduced airflow, it's best to call in an HVAC professional to diagnose and repair the problem. Attempting complex repairs on your own can be dangerous and may end up causing more damage if not done properly.