DIAGNOSIS The F1 error code is a temperature sensor fault. The fryer's internal sensor isn't reading correctly, so it shuts down to prevent unsafe operation.
FIX Unplug the unit and let it cool completely for at least 30 minutes. Remove the basket and tray. Check the heating element chamber for any large, obvious food debris blocking the sensor (a small probe near the top of the chamber). Clean it out with a dry brush. Plug it back in empty and try a test run at 350°F for a few minutes.
IF THAT DIDN'T WORK The sensor itself may have failed. With the unit unplugged and cool, inspect the thin wire leading to the sensor probe for any visible damage or disconnection. If you see damage, the unit needs service. For most users, this persistent F1 means a hardware failure requiring a warranty claim.
HEADS UP Do not attempt to bypass this error or run the unit with the F1 code displayed. It's a critical safety sensor. Repeatedly getting F1 after a thorough clean-out is your signal to contact Chefman support.