1, the reason why the electric lunch box doesn't work when powered on is that the power-on time is too short; Ambient temperature, the temperature of rice, vegetables and soup is too low. Extend the boot time appropriately. Either there is too much scale on the electric heating tube, resulting in local high temperature, and the heating unit has thermal protection. You can try to remove the scales and try again. If it still can't be solved, there is something wrong with the thermal protection system of the heating device and it must be repaired.
2. The power indicator goes out and the voltmeter does not display. Check whether the air switch is closed and the fuse of the control line is intact. If the temperature of the electric heater does not rise, check whether the fuse is intact, whether the thermal resistance (thermocouple) is connected correctly, and whether the heating element is damaged.