Diagnosis
Loose components or a failing fan motor/bearing. The most common source is the blower wheel coming loose on its shaft or having debris stuck in it.
How to Fix It
Secure the blower wheel.
- Power off at the breaker.
- Remove the service panel to access the blower assembly.
- Check the set screw on the blower wheel hub where it attaches to the motor shaft. Tighten it firmly.
- Spin the wheel by hand to check for debris (like a stray screw) and listen for grinding.
If That Didn't Work
The noise may be from the condenser fan (the one near the compressor). Its blade could be cracked or hitting the shroud. Inspect it for damage and ensure its mounting is tight.
Heads Up
If the noise is a high-pitched whine or screech, it's likely a dry motor bearing. The motor will need lubrication or replacement soon. Don't ignore rattling—a loose blower wheel can eventually damage the motor shaft.