De'Longhi dehumidifier displays E3 and shuts down compressor operation.

Safety first: Unplug the unit before removing the control panel or front grille.

Step-by-step:

• 1. Confirm symptom: Verify that E3 appears shortly after power-on and that humidity setpoints cannot be adjusted properly.
• 2. Access the control panel area: Remove screws securing the top or front panel to expose the display board and main PCB.
• 3. Locate the humidity sensor: On many De'Longhi dehumidifiers, the humidity sensor is a small module near the air intake grille or mounted on a small daughterboard connected to the main PCB.
• 4. Check connections: Reseat the humidity sensor connector on the PCB. Look for corrosion or moisture damage around the connector.
• 5. Inspect sensor placement: Ensure the sensor is not blocked by plastic film, dust, or foam. Gently clean dust with a soft brush; do not use liquid cleaners on the sensor element.
• 6. Replace the humidity sensor: If E3 persists, replace the humidity sensor module with the correct De'Longhi part. Mount it in the same location to ensure accurate readings.
• 7. PCB replacement: If a new sensor does not resolve E3, the main control board is likely faulty and should be replaced by a qualified technician.