Your boiler has detected an internal electrical fault with the component that controls the gas supply, meaning it cannot safely ignite for heating or hot water.

Gas valve relay error

What causes this fault?

This fault occurs when the boiler's main control board detects a communication failure or a physical defect in the relay that triggers the gas valve. Effectively, the brain of the boiler can no longer safely tell the gas valve to open or close, so it shuts down as a safety precaution. The most common reason is internal wear and tear on the printed circuit board's electrical components or a fault within the gas valve's solenoid.