Dehumidifier displays E4 and shuts down shortly after starting

Safety: Unplug the unit before cleaning or opening. Do not attempt to open the sealed refrigeration system.

Steps:

• Check airflow: Remove and clean the air filter with mild soap and water; let it dry completely. Inspect the front and rear grilles for dust buildup and vacuum them.
• Clear obstructions: Ensure at least 12–18 inches of clearance around the unit. Do not place it flush against walls or furniture.
• Inspect coils: Remove the bucket and front grille. If accessible, visually inspect the evaporator (front) and condenser (rear) coils. Clean gently with a soft brush or coil cleaner if heavily clogged.
• Sensor check: Locate the evaporator and condenser thermistors (if separate) and ensure they are firmly attached to the tubing and their wiring is intact. Reseat their connectors on the control board.
• Reset and test: Reassemble, plug in, and run the unit in a cool, well-ventilated room. If E4 returns quickly, a sensor or control board may be faulty.
• Do not attempt refrigerant repairs: If coils are icing heavily or the compressor is extremely hot, the sealed system may be compromised. This requires a certified technician.

When to call for service: Persistent E4 after cleaning and sensor checks usually indicates a bad sensor or control board, or a sealed system problem that must be handled professionally.