Dehumidifier stops and displays E4, often after running for a short time

Safety: Unplug the unit. Do not attempt to open the sealed refrigeration system (compressor, refrigerant lines).

• Allow unit to thaw: If the evaporator is iced over, leave the unit unplugged with panels open for several hours until all ice melts. Restart and see if E4 returns.
• Locate defrost sensor: Some Inventor models use a dedicated defrost NTC sensor clipped to the evaporator or discharge line. Verify it is firmly attached and not dangling.
• Inspect sensor and wiring: Look for broken insulation, loose connectors, or corrosion. Reseat the connector on the PCB.
• Test sensor resistance: With the unit unplugged, measure resistance of the defrost sensor and compare to the ambient sensor at similar temperature. A reading of 0 Ω or infinite indicates failure.
• Replace defrost sensor: Install a new Inventor defrost NTC sensor if the original is defective.
• Persistent E4: If the sensor is good and E4 persists, there may be a deeper refrigeration or PCB issue (e.g., low refrigerant, blocked capillary, faulty compressor). Contact a qualified refrigeration technician; do not attempt sealed system repairs yourself.