Humidifier will not start, display shows F0 immediately after plugging in or pressing power.

Safety first: Unplug the humidifier before opening any covers. Never work on the unit while it is connected to power.

Steps to try:

• Power reset: Unplug the unit for 10 minutes, then plug back in and try again. Sometimes F0 is a transient communication error.
• Check external conditions: Make sure the unit is not in a very cold or very hot environment (typically 5–40°C). Extreme temperatures can cause sensor errors.
• Inspect sensor harness: If you are comfortable removing the housing, locate the small humidity/temperature sensor board near the air outlet grille. Check that its multi-pin connector is fully seated on the main control PCB and that no wires are pinched or broken.
• Clean sensor area: Use a soft brush or compressed air to remove dust from the sensor board and air path. Do not spray liquids directly on the sensor.
• If F0 persists: The main control PCB or sensor module is likely defective. Replacement requires opening the cabinet and transferring wiring harnesses correctly. If you are not experienced with electronics, contact a Rowenta-authorized service center.