Microwave runs but does not heat; after several seconds E03 appears on the display.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Critical safety warning: The high-voltage section of a microwave (transformer, capacitor, diode, magnetron) can be lethal. The capacitor can retain a dangerous charge even after unplugging. Do not attempt high-voltage testing or replacement unless you are trained and have proper tools and procedures for safely discharging the capacitor.
User-level checks:
- 1. Confirm symptom: Place a cup of water inside and run for 1–2 minutes. If the turntable rotates and the light is on but the water remains cold and E03 appears, the control is detecting a heating fault.
- 2. Check power supply: Ensure the microwave is plugged directly into a properly grounded outlet (no extension cords). Verify the outlet voltage is correct using a plug-in tester or multimeter.
- 3. Listen for high-voltage hum: When starting, a normal microwave produces a low humming sound from the transformer/magnetron. If this is absent or unusually loud/buzzing, a high-voltage component may be failed.
Technician-level actions (for professionals only):
- Discharge the high-voltage capacitor safely.
- Test the high-voltage diode and capacitor with appropriate meters.
- Check transformer primary and secondary windings for continuity and shorts.
- Test magnetron filament continuity and inspect for arcing or cracks.
Recommendation: Due to the risk involved, E03 faults should be handled by a Sharp-authorized technician. Replacement of the magnetron, transformer, or capacitor must use Sharp-approved parts.