Warning: Unplug the microwave. Internal components can remain charged; avoid the high-voltage section.

Check vents: Ensure all exterior vents (top, front, and rear) are clear of grease filters, dust, or obstructions. Clean grease filters in warm soapy water and dry completely.
Listen for fan: When the microwave is running (before F8 appears), listen for the internal cooling fan. If you do not hear it, the fan may have failed.
Inspect fan area (advanced): With the outer cover removed (if you are qualified), check that the fan spins freely and that no wiring is loose.
Thermostat check: Some GE models use a thermostat or thermal cutout in series with the fan. If open, the fan will not run and F8 may appear. Testing requires a multimeter and should be done by a technician.
Replace failed parts: Replace the internal cooling fan motor or thermostat/thermal cutout as needed. If the fan and thermostat are good, the control board fan relay may be defective.

Microwave displays F8 and may not start or may stop during sensor cooking cycles.

Possible Causes