DIAGNOSIS That’s usually the sound of the cooling fan hitting an obstruction. Over time, crumbs or bits of food can get pulled into the rear vent area where the fan is located.
FIX Safety first: unplug the unit and let it cool. 1) Unplug it. 2) Tilt the unit forward gently and look at the rear ventilation slots. 3) Use a can of compressed air (like for cleaning keyboards) to blow out any visible debris from the vents. Hold the can upright and use short bursts. 4) You can also use a soft brush, like a clean paintbrush, to dislodge any larger pieces. 5) Plug it back in and test. The noise should be gone.
IF THAT DIDN'T WORK If the grinding persists, it’s possible a fan blade itself is damaged or the motor bearing is failing. This is less common but can happen if something hard was sucked in. At this point, you’d need to contact Chefman customer support.
HEADS UP Try not to use the air fryer on a counter directly against a wall. Leave a few inches of space behind it for proper airflow, which also helps keep crumbs from getting sucked into the vent.