BoilerFaultCodesTechnical description
Failure of thermocouple, power unit or latching mechanism
What causes this fault?
This fault occurs when the boiler's safety system can no longer detect the small permanent flame used to light the main burner. The most common reason is that the heat-sensing probe has worn out over time or the internal magnetic switch within the gas valve has failed, causing the gas supply to shut off for safety. Without this pilot light being confirmed as active, the boiler is prevented from firing up entirely.
This issue is frequently noticed during the first cold spell of autumn when the boiler is worked harder after being mostly idle during the summer months.
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.