Your boiler is unable to correctly control the supply of gas it needs to create a flame, causing the system to shut down for safety.

Gas mechanism fault

What causes this fault?

This fault occurs when the boiler's control board fails to communicate effectively with the gas valve, meaning the system cannot safely regulate the fuel flow. The most common reason is an internal electrical failure within the gas valve itself or a fault on the main circuit board that prevents it from sending the correct signals. In some cases, damaged or loose wiring between these two major components is responsible for the breakdown.