Beurer ultrasonic humidifier shows E4 and shuts down shortly after starting.

Safety: Unplug the unit and allow it to cool for at least 20 minutes before inspection.

Steps to resolve:

• Check airflow: Ensure that the air outlet and intake grills are not blocked by walls, curtains, or dust. Maintain at least 20–30 cm clearance around the unit.
• Clean vents: Use a soft brush or vacuum with a brush attachment to remove dust from all grills and openings.
• Verify fan operation: Turn the unit on briefly (with covers in place) and listen for the fan. If the fan does not run or is very weak, unplug and inspect the fan area for obstructions.
• Inspect the fan: Remove the housing to access the fan. Check for hair, lint, or debris wrapped around the fan blades or shaft. Clean carefully and ensure the fan spins freely by hand.
• Check thermal protection devices: Many Beurer units have a small thermal fuse or thermostat attached to the heater or PCB heatsink. If the unit overheated previously, this component may have opened permanently and must be replaced with the exact rating.
• Reassemble and test: After cleaning and verifying fan movement, reassemble the unit, restore power, and test. If E4 reappears quickly, discontinue use.

Important: If you suspect a failed thermal fuse or thermostat and are not experienced with electrical repairs, contact a qualified technician. Bypassing safety devices is dangerous.