DIAGNOSIS: Something is interfering with the convection fan blade at the back of the oven. It's usually food debris or a loose piece of foil, or the fan motor bearing is failing.
FIX:
- Remove oven racks and the metal convection cover at the very back wall of the oven interior. It's held by one or two screws.
- Inspect the fan blade for any obstructions—bits of foil, burnt food, etc. Remove them carefully.
- Manually spin the blade. It should rotate freely and silently. If it grinds or feels rough, the motor assembly likely needs replacement.
- If clear, reassemble and test.
IF THAT DIDN'T WORK: If the noise persists with the blade clear, the fan motor bearings are shot. You'll need to replace the entire convection fan motor assembly, which is accessed from the rear panel of the range.
HEADS UP: Never cover the convection fan area with aluminum foil to "catch spills." It can melt onto the fan or motor and cause this exact problem, or worse, a short.