Microwave runs (light and fan on) but does not heat food; E03 appears on the display after a short time.

Critical safety warning: The high-voltage section of a microwave (transformer, capacitor, diode, magnetron) can store and generate lethal voltages. Do not attempt to service these components unless you are a trained technician with proper tools and procedures for discharging capacitors.

User-level checks:

• Confirm that you are using microwave-safe cookware and that the load is not extremely small (e.g., running empty), which can stress the high-voltage system.
• Try heating a large mug of water for 2–3 minutes. If there is no warmth and E03 appears, the issue is internal.

Technician-level outline (for reference only):

• Unplug the unit and safely discharge the high-voltage capacitor using an appropriate resistor and insulated tools.
• Inspect the high-voltage diode for visible damage or burning and test it with a high-voltage diode test method or appropriate meter.
• Test the high-voltage capacitor for capacitance and insulation resistance; replace if shorted or open.
• Check the primary and secondary windings of the high-voltage transformer for continuity and correct resistance.
• Test the magnetron filament for continuity and check for shorts to ground.

Recommendation: Due to the danger and specialized tools required, contact a Hoover-authorized service center for any E03 high-voltage fault.