Dehumidifier shows E4 and shuts down or fails to start the compressor.

Safety: Unplug the unit before opening the cabinet.

Steps:

• Allow thawing: If the evaporator coil is iced over, unplug the unit and let it thaw completely (this can take several hours). Place towels under the unit to catch water.
• Access the evaporator: Remove the front grille and any internal covers to expose the evaporator coil.
• Locate the defrost sensor: It is usually clipped to the evaporator coil tubing or attached with a metal clip or tape. It may look like a small cylindrical or bullet-shaped sensor.
• Check attachment and condition: Ensure the sensor is firmly attached to the coil and not hanging loose. Inspect for cracks, corrosion, or broken wires.
• Inspect wiring harness: Follow the sensor wires to the control board. Reseat the connector and check for damage along the harness.
• Test after thaw: Once fully thawed and reassembled, plug in and run the unit. If E4 returns quickly, the defrost sensor is likely faulty and should be replaced.
• Board evaluation: If a new defrost sensor does not resolve E4, the main control board may be misreading the sensor and should be evaluated by a professional.