Dehumidifier displays E4 and stops; may occur after running for a short time.

Safety: Unplug the unit. Coils and metal edges can be sharp; wear gloves.

Steps:

• Access coil area: Remove front cover and filter to expose the evaporator coil.
• Identify defrost sensor: Some Tosot models use a dedicated defrost thermistor clipped to the lower part of the evaporator or suction line. It may share function with the evaporator sensor; consult your manual if available.
• Check attachment: Ensure the sensor is firmly clipped and making good thermal contact with the tubing. Reclip or secure with aluminum tape if loose.
• Inspect wiring: Look for broken insulation, pinched wires, or loose connectors between the sensor and PCB.
• Test sensor: With a multimeter, measure resistance at room temperature and compare to expected NTC values. If open/shorted, replace the defrost temperature sensor.
• Board evaluation: If sensor and wiring are good but E4 persists, the main control board’s defrost logic may be faulty and require replacement.