Aquabion softener shows E19 and the controller reports an internal temperature over-limit.

Safety first: Unplug the unit before relocating or opening the controller.

• Check installation environment: Ensure the Aquabion softener is not installed in direct sunlight, next to a boiler, or in a sealed cabinet without ventilation.
• Improve ventilation: Provide adequate airflow around the controller by opening cabinet doors, adding vents, or relocating heat sources.
• Inspect electronics: Remove the controller cover and look for signs of overheating (discolored PCB, melted plastic). If present, replace the main control board.
• Sensor check: If the environment is cool but E19 persists, test or replace the controller temperature sensor if it is a separate component.

Warning: Do not drill ventilation holes in the controller housing itself; this can expose live parts and void safety certifications.