How to Fix / Troubleshooting

Safety first: Unplug the microwave before inspection.

Inspect the cavity and waveguide cover: Open the door and locate the mica or plastic waveguide cover on the side or top interior wall. Look for burn marks, holes, or carbonized food deposits.
Clean the cavity: Wipe the interior with a mild detergent solution and a soft cloth. Remove all food splatters, especially near the waveguide cover. Do not use metal tools.
Replace damaged waveguide cover: If the cover is burnt, cracked, or has holes, replace it with a Zanussi-compatible waveguide cover cut to the same size and shape.
Test operation: After cleaning and replacing the cover, test with a cup of water. If E04 persists or arcing continues, the magnetron or waveguide channel may be damaged.

Internal waveguide or magnetron replacement should be performed only by a qualified technician due to radiation safety requirements.

Microwave stops and displays E04 shortly after starting, often accompanied by a humming noise and no heating.

Possible Causes