Error 09; appliance locks out and may show abnormal temperature readings.

Safety: Isolate electrical power and close water valves if removing any wet components.

Steps:

• Locate DHW NTC: Find the sensor on the domestic hot water outlet or on the plate heat exchanger.
• Inspect and clean: Check for corrosion or scale around the sensor. Remove and clean the sensor tip and pocket if accessible.
• Check wiring: Ensure the sensor cable is intact and firmly connected to the control board.
• Test or replace: If you have a multimeter, test resistance versus temperature. If readings are erratic or out of spec, replace the DHW NTC sensor.

Tip: After replacement, verify that the displayed hot water temperature is realistic when running a tap.