Your boiler is failing to light the fuel or keep the burner running, meaning it is not producing any heat or hot water.

Flame Failure

What causes this fault?

This fault occurs when the boiler attempts to light the burner but cannot detect a stable flame. The most common reasons include a worn-out sensor that can no longer 'see' the fire, a blockage in the gas supply, or an electronic failure that prevents the initial spark from occurring.