Microwave stops heating and displays E21 during operation.
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: Microwaves contain lethal high voltage. Unplug the unit and do not touch internal components unless you are trained and have discharged the high-voltage capacitor properly. For most users, this repair should be left to a professional.
User-level checks:
- Ventilation: Ensure that all ventilation openings on the sides, top, and rear are clear of obstructions. Built-in Electrolux microwaves must have proper cabinet clearances as specified in the installation manual.
- Cooling fan sound: Start a short cook cycle with a cup of water. Listen for the internal cooling fan. If the fan is not running but the turntable moves and light is on, the unit may be overheating internally.
- Power reset: Unplug the microwave for 5–10 minutes to allow internal thermostats to reset, then test again. If E21 reappears quickly, internal components are likely faulty.
Technician-level diagnostics:
- Check continuity of the magnetron thermal cut-out (TCO) and cavity thermostat.
- Test the magnetron for shorts to ground and open filament.
- Verify operation of the cooling fan motor and that air channels are not blocked by grease or insulation.
- Inspect the high-voltage wiring harness and connectors to the magnetron and high-voltage transformer or inverter board.
Because of the high-voltage risks, contact an authorized Electrolux service center for magnetron or TCO replacement.