DIAGNOSIS The fan blade at the top of the cooking chamber is hitting a loose object or is misaligned. A loose screw or a small piece of food can cause this.
FIX Unplug the fryer. Remove the fry basket and bowl. Use a flashlight to look up into the heating chamber. Look for any loose food debris. Check if the central fan blade can wobble side-to-side. Tighten any visible mounting screws for the fan assembly.
IF THAT DIDN'T WORK The fan motor bearings may be worn out. The motor is not a user-serviceable part. You need to contact Nutrichef for a motor replacement or a warranty claim.
HEADS UP Do not operate the fryer with this noise. A damaged fan can cause uneven cooking and is a potential fire hazard.