Microwave runs (light and fan on) but does not heat; display shows E03 after a few seconds.
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 (HV) section of a microwave (transformer/inverter, capacitor, diode, magnetron) can store and generate lethal voltages. Do not attempt HV repairs unless you are specifically trained and equipped. The steps below are limited to safe user checks.
User-level checks:
- Confirm that the unit is not in a low-power or defrost mode by mistake. Test on full power (100%) with a cup of water for 1–2 minutes.
- Listen for the normal hum of the magnetron/transformer. If the sound is unusually quiet or different, note this for the technician.
- Unplug the microwave for 10 minutes to reset the control board, then test again.
When to stop: If E03 returns and the oven still does not heat, internal HV components are likely faulty. Do not continue to run the microwave, as this can damage additional parts.
Technician actions (for reference):
- Test the high-voltage fuse and replace if open, investigating the root cause.
- Check the HV transformer or inverter module for correct output.
- Test the magnetron for shorts or open filament.
- Inspect the HV capacitor and diode for shorts or leakage.
Due to the danger involved, contact an authorized SMEG service center for diagnosis and repair.