DIAGNOSIS That's the fan motor bearing or the fan itself. The most common culprit is a small piece of food debris (like a breadcrumb or seed) stuck in the fan blades or housing near the heating element.
FIX
- Unplug the unit and let it cool completely.
- Remove the drawer and basket.
- Look up into the heating chamber. Use the light on your phone to inspect the silver heating element and the black fan housing directly above it.
- Use a dry, soft-bristle brush (a clean paintbrush works) or a can of compressed air to gently dislodge any visible debris. Do NOT use anything metal or sharp.
IF THAT DIDN'T WORK The noise could be from the internal fan motor bearing wearing out. If the noise is constant and grinding, and cleaning did nothing, the motor assembly is likely failing. Contact Ninja customer support at this point.
HEADS UP Never spray water or cleaner directly into the heating chamber where the fan is. You can damage the electrical components. Only clean when unplugged and cool.