Microwave runs but does not heat food, display shows E03.
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. Do not attempt internal repairs unless you are a trained appliance technician with proper tools and procedures for discharging the capacitor.
User-level checks:
- 1. Confirm symptom: Place a cup of water inside and run on full power for 1–2 minutes. If the turntable rotates and light is on but the water remains cold and E03 appears, heating has failed.
- 2. Check power level settings: Ensure the power level is not set to 0% or a very low level. Reset to 100% and test again.
- 3. Power reset: Unplug the microwave for 5 minutes, then reconnect and test. If E03 returns, an internal component is likely faulty.
Technician-level actions:
- Test magnetron continuity and insulation.
- Measure high-voltage transformer primary and secondary windings.
- Check high-voltage diode and capacitor with appropriate test equipment.
- Replace the magnetron or high-voltage transformer as indicated by diagnostics.
Due to the risks, contact a Siemens-authorized service center for E03 faults.