Dehumidifier displays E4 and shuts down; compressor will not start.

Safety: Unplug the unit. Do not attempt to open the sealed refrigeration system yourself; refrigerant work requires a licensed technician.

• Basic reset: Unplug for 15 minutes, then restart. If E4 returns quickly, continue.
• Check airflow: Remove and clean the air filter with mild soap and water; dry completely. Inspect the evaporator and condenser coils for heavy dust or lint and gently vacuum with a soft brush.
• Inspect coil sensor: Access the evaporator area and locate the defrost/coil sensor or thermal fuse clipped to the tubing. Ensure it is firmly attached and the wires are intact.
• Room conditions: Ensure the unit is used within the specified temperature range (typically 41–95°F / 5–35°C). Very low room temperatures can cause coil freeze and trigger E4.
• Sensor replacement: If the coil sensor tests open or shorted with a multimeter, replace it with the correct Comfee defrost/coil temperature sensor.
• Refrigerant/system issues: If airflow is good and sensors are OK but E4 persists, the sealed system may be undercharged or restricted. This requires a professional HVAC/appliance technician to diagnose and repair.