BoilerFaultCodesTechnical description
Main burner fails to light and pilot is extinguished when pressure on the control knob is released - Control knob not held down long enough.
What causes this fault?
This fault occurs when the safety system, centered around a part called a thermocouple, fails to detect a stable flame. When you release the ignition button, the boiler shuts off gas flow because it incorrectly believes the pilot light has gone out, or the components responsible for holding the gas valve open have physically worn out. The most common reason is a deteriorated thermocouple tip that can no longer generate the tiny electrical pulse needed to keep the boiler running.
This issue is frequently seen during the first cold spell of autumn when the boiler is switched back on after being idle throughout the summer.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.