| F.28 | Ignition fault on start-up. | The misadjusted or faulty gas valve does not open/modulate the correct flow, preventing the flame from being generated or ionised; check inlet/outlet pressure and MIN/MAX adjustment with a manometer and measure continuity/ohmage of coils and power supply to the valve. |
| F.61 | Error: gas valve control. | The electronics detect a fault in the operation of the valve (coils shorted/grounded, faulty valve, or defective wiring); check the harness to the valve, coil resistance, and ensure the valve responds to the PCB control board. |
| F.62 | Error: gas valve disconnection controller. | Delayed closure or non-sealing of the valve after flame extinction; verify that the valve shuts off immediately (tightness test/manometer) and rule out a jammed valve or internal leakage. |
| F.88 | Fault in the gas valve. | The boiler detects a gas valve not connected/poorly connected or faulty; check connectors, polarity, and coil continuity, and replace the valve if it does not operate. |