| F1 | Ignition fault (flame not established). | If the gas valve does not open or opens insufficiently during the ignition attempt, no gas reaches the burner and the boiler locks out due to lack of flame. Check the power supply to the coils/solenoids and pressure at the valve inlet during start-up. |
| F6 | Flame detected with burner off (parasitic flame). | An incomplete closure of the gas valve may allow gas to pass through and maintain a residual flame after shutdown. Check the tightness/closure of the on-off valves of the gas valve and ensure the flame extinguishes when cut off; perform a leak test and closure test on the valve itself. |
| F10 | Fault in the gas valve control. | The electronics command the solenoid valves to close/open, and the valve does not respond (coil/relay fault) or does not close properly; the system detects it and locks. Check continuity and consumption of the coils, commands from the PCB, and effective closure by measuring pressure at the valve port during the shutdown cycle. |