Your boiler has detected a critical internal error that prevents it from operating safely, so it has shut itself down to protect your home.

Boiler fault. Call engineer.

What causes this fault?

This fault occurs when the boiler's internal sensor can no longer accurately monitor the temperature of the water heading to your taps. Over time, these sensors can degrade due to constant temperature changes or develop electrical faults, causing the boiler to shut down the hot water as a safety precaution.