F4
Medisana
Overheat Protection / Base Temperature Sensor Fault
Humidifier displays F4; unit may shut down shortly after starting mist.
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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.
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Possible Causes
Blocked air vents causing overheating, Failed base NTC temperature sensor, Dust buildup around electronics, Defective overheat protection circuit on PCB
How to Fix / Troubleshooting
Safety: Unplug the humidifier and let it cool completely before inspection.
- Ventilation: Ensure the unit is placed on a hard, flat surface with at least several centimeters of clearance around all vents. Remove any objects blocking airflow.
- Clean vents: Use a soft brush and vacuum to remove dust from intake and exhaust grilles.
- Inspect base sensor: Open the base housing and locate the NTC sensor attached to the PCB or near the transducer. Check that it is firmly attached and not burnt or broken.
- Replace sensor: If the sensor is damaged or tests open/short, replace it with the correct base NTC sensor for your Medisana model.
- PCB fault: If F4 persists with a good sensor and proper ventilation, the overheat circuit on the main PCB is likely faulty and the board should be replaced.
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Repair Difficulty
Medium
3/5
Required Part
Base NTC Temperature Sensor
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