Microwave shows F1E4 and will not heat; sometimes accompanied by a humming sound stopping quickly.

Critical Safety: Inverter-based microwaves operate at very high voltage. Do not attempt to test the inverter or magnetron energized unless you are a trained technician. Always unplug the unit and allow several minutes for discharge.

• Visual inspection: Remove the outer cabinet (if accessible on your installation) and inspect the inverter board for burn marks, cracked components, or a burnt smell.
• Check wiring: Verify all harnesses between the main control board, inverter board, and magnetron are firmly connected and not heat-damaged.
• Door interlocks: Confirm the door closes properly and latches fully; a misaligned door can sometimes cause inverter-related errors.
• Component replacement: If F1E4 persists, the inverter board is the most common failure. However, a shorted magnetron can also trigger this code. Many technicians replace both the inverter board and magnetron together on older units to ensure reliability.
• Professional service recommended: Due to lethal voltages, replacement of the inverter and magnetron should be done by a qualified appliance technician.