How to Fix / Troubleshooting

Safety: Unplug the humidifier and allow it to cool completely before inspection.

Steps:

Check that the air and mist outlets are not blocked by objects, dust, or scale. Clean as needed.
For warm-mist or evaporative models, verify that the internal fan is running when the unit is on. If not, inspect and replace the fan motor if seized or open-circuit.
Open the base (if serviceable) and locate the thermal fuse or thermostat attached to the heater or main PCB area. Test continuity; a blown thermal fuse must be replaced with the same rating.
Descale any heating elements or internal surfaces using manufacturer-approved descaling solution or diluted vinegar, then rinse thoroughly.
After replacing any safety device, reassemble and test. If F3 recurs, discontinue use and have the unit inspected professionally, as there may be a design-level overheating issue.

Humidifier displays F3 and shuts down; may coincide with overheating of base

Possible Causes