Microwave stops and displays E04; interior light and fan may continue briefly before shutting down.

Safety: Unplug the microwave before removing any covers. Allow the unit to cool completely.

Initial checks:

• 1. Allow cooling: Leave the door open and let the microwave cool for at least 30 minutes. Then plug it back in and test with a short 30-second cycle. If E04 does not return, the error may have been due to temporary overheating.
• 2. Check ventilation: Ensure that the Blomberg microwave has the required clearance around it and that vents are not blocked by cabinets, walls, or other appliances. Clean dust and grease from vents.
• 3. Avoid long, high-power cycles: When cooking for extended periods, use lower power levels or intermittent operation to reduce cavity temperature.

Advanced checks:

• 4. Inspect cavity temperature sensor: Unplug the unit and remove the outer cabinet. Locate the cavity temperature sensor (NTC) usually mounted on the top or side of the cooking cavity. Check for loose connectors or damaged wiring.
• 5. Test sensor: Use a multimeter to measure the sensor resistance at room temperature and compare with Blomberg specifications. Replace the sensor if it is open, shorted, or far out of range.
• 6. Control board: If the sensor and wiring are good but E04 persists, the control PCB may be misreading the sensor. Board replacement should be done by a professional.