Microwave runs but does not heat; display shows E3 after a few seconds.

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 when unplugged. If you are not specifically trained in microwave high-voltage repair, do not attempt this repair. Contact a qualified technician.

For trained personnel only:

• 1. Discharge the capacitor: After unplugging the unit, use an insulated resistor discharge tool to safely discharge the high-voltage capacitor according to professional procedures.
• 2. Inspect components visually: Look for burned terminals, cracked capacitor casing, or signs of arcing around the magnetron and high-voltage wiring.
• 3. Test high-voltage diode: Using a multimeter with diode test, check the HV diode for one-way conduction. Replace if shorted or open.
• 4. Test capacitor: Use a capacitance meter or an analog meter with proper HV capacitor test procedure. Replace if shorted, open, or out of specification.
• 5. Check transformer and magnetron: Test primary and secondary windings of the HV transformer for continuity and shorts to ground. Test magnetron filament continuity and check for shorts to chassis. Replace any defective component with the correct Avanti part.

If you are not fully comfortable with these steps, do not proceed. Have the microwave serviced by a professional.