Boiler displays E06, domestic hot water (DHW) temperature is incorrect or not regulated.

Safety: Turn off power and close water valves to the boiler if you need to remove any wet components.

• Locate DHW sensor: On combi Klimosz boilers, the DHW NTC is usually clipped to the plate heat exchanger; on system boilers with cylinder, it may be inserted into a tank pocket.
• Check connection: Ensure the sensor plug is fully seated on the control board and at the sensor end. Clean any oxidation with contact cleaner.
• Measure sensor: Disconnect the sensor and measure resistance with a multimeter. Compare with Klimosz NTC chart. Replace if out of specification.
• Inspect cable routing: Ensure the cable is not pinched between panels or touching hot flue parts which can melt insulation.
• Test operation: After replacing or reseating the sensor, restore power and run a hot water tap. Confirm that the temperature is stable and E06 does not reappear.