Aprilaire dehumidifier shows E3 and shuts down

Safety first: Disconnect power before removing panels or filters.

• Check airflow: Inspect the return air filter (if equipped) and clean or replace it. Ensure the intake and discharge grilles are not blocked by furniture, dust, or duct restrictions.
• Inspect fan operation: Restore power briefly and observe if the blower/fan runs when the unit calls for dehumidification. If the fan does not start, the compressor may overheat and trigger E3.
• Clean coil: With power off, inspect the evaporator and condenser coils for heavy dust buildup. Gently vacuum with a soft brush or use coil cleaner approved for aluminum fins.
• Check temperature sensor: Locate the high-temperature or coil sensor and ensure it is firmly attached to the coil or discharge line. Loose sensors can misread temperature.
• Professional service: If airflow is good and the fan runs but E3 persists, the unit may have a refrigerant or compressor issue. Contact a qualified HVAC technician to check refrigerant charge and system pressures.