Overheat Lockout

A boiler fault code alone is not a gas or carbon-monoxide emergency. If you smell gas, a CO alarm sounds, or someone has possible carbon-monoxide symptoms, leave and call 0800 111 999 from outside.

Safe check: Switch the boiler off and let it cool. Use the filling loop to raise pressure to 1.0 bar, check that radiator valves are open, then restart once.

Gas Safe registered engineer: The message remains or returns after one restart; arrange a Gas Safe registered engineer.