Microwave displays E4 and stops heating; internal light and turntable may still operate.

Critical safety warning: The high-voltage section of a microwave can exceed 4,000 volts and remains charged even when unplugged. Only experienced technicians should work on these parts.

• Basic user checks (safe):
  • Unplug the unit for 5–10 minutes and plug back in to see if the code clears.
  • Ensure the outlet is properly grounded and not shared with heavy loads.
• Technician-level checks:
  • Remove the cabinet and visually inspect the high-voltage capacitor, diode, and transformer for burn marks, bulging, or melted insulation.
  • Test the high-voltage diode with a multimeter that has a diode test function (after safely discharging the capacitor). Replace if shorted or open.
  • Test the capacitor for shorts to ground and capacitance value using an appropriate meter.
  • Check transformer primary and secondary windings for continuity and signs of overheating.

Recommendation: For most homeowners, replacement of the entire microwave is safer and more economical than DIY HV repair.