Worcester Bosch FA306 Fault Code

What causes the Worcester Bosch FA306 fault?

This fault occurs when the boiler's internal safety sensors continue to detect a flame signal even after the unit has been told to stop burning gas. The most common reason is a faulty sensor or a sticking gas valve that isn't closing properly, posing a safety risk that requires the system to shut down immediately. Over time, moisture or carbon buildup on the electrodes can also cause the control board to 'see' a ghost signal that isn't actually there.