Boiler locks out with E06, domestic hot water (DHW) temperature is incorrect or not displayed, burner may not fire on hot water demand.

Safety first: Turn off power and close the cold water inlet if you need to remove any DHW components. Hot water can cause scalding—allow the boiler to cool.

Step-by-step checks:

• 1. Check DHW temperature reading: If the display shows unrealistic DHW temperatures (e.g., 0°C or 99°C when tap is off), suspect the DHW NTC.
• 2. Inspect sensor and wiring: Locate the DHW NTC on the domestic hot water outlet or plate heat exchanger. Ensure the sensor is fully inserted and the connector is tight and free of corrosion.
• 3. Descale sensor pocket: If accessible, remove the sensor and inspect for limescale. Clean gently with descaling solution and rinse thoroughly before refitting.
• 4. Resistance check (optional): With power off, measure the NTC resistance and compare with Viadrus data. Replace if out of range.
• 5. Reset boiler: After any work, restore power and reset. Test hot water at a tap to confirm stable temperature and that E06 has cleared.

When to stop: If the sensor tests correctly but the boiler still shows E06, the control board may be faulty and should be checked by a professional.