DIAGNOSIS: Excessive fan noise. This is almost always caused by a loose or warped fan blade on the blower wheel, or debris caught in the housing.
FIX: Remove the grease filter and inspect the blower wheel behind it. Look for any obvious obstructions (e.g., a utensil, packaging debris). If clear, the blower wheel itself is likely the issue. On this model, the plastic wheel can warp or its mounting hub can crack, causing an imbalance. You'll need to remove the vent cover to access and replace the blower wheel assembly.
IF THAT DIDN'T WORK: The fan motor bearings could be worn out. A failing motor will have a grinding or high-pitched whine in addition to the loud volume. Motor replacement involves disassembling the top cabinet.
HEADS UP: Don't just ignore a loud fan. An imbalanced blower wheel puts extra stress on the motor and can lead to a complete—and more expensive—motor failure.