BoilerFaultCodesTechnical description
Main burner fails to light and pilot is extinguished when pressure on the control knob is released - Failure of thermocouple, power unit or latching mechanism.
What causes this fault?
This fault occurs when the boiler's safety circuit fails to detect a constant, healthy pilot flame, causing it to shut off the gas supply for safety. The most common reason is a worn-out thermocouple that can no longer generate the tiny electrical current needed to hold the gas valve open, though it can also be caused by a faulty magnetic latch within the valve itself.
This issue is frequently noticed during the first cold spell of autumn when the boiler is switched back on after being idle over the summer, as debris can build up around the pilot light.
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.