Your boiler has temporarily stopped working because it has detected that dangerous exhaust fumes are not being cleared away safely.

Technical description

Temporary Shutdown Due To Defective Discharge of Exhaust Fumes. The boiler is fitted with safety devices, which in the event of a defective discharge of exhaust fumes, automatically interrupts the gas supply. The shut-off is temporary and is indicated by the illumination of the yellow L.E.D. E for a period of about 15 minutes.