| F26 | Fault in the stepper motor of the gas valve. | The actuator (stepper) of the valve does not respond or does not provide feedback; check continuity/ohms of coils, connectors, and control voltage from the PCB. If the coils are out of range or there is no movement, replace the valve. |
| F27 | Incorrect flame detection (flame when there shouldn't be). | The gas valve may leak or not close completely, causing an ionisation signal with the burner 'off'; check the valve's tightness/closing time and rule out moisture/electronics before replacing it. |
| F28 | Ignition fault (won't start). | If the gas valve does not open or opens out of point, gas does not reach the burner; check the inlet pressure, control signal to the valve, and operation in ignition/diagnostic test before replacing it. |
| F61 | Fault in the operation/command of the gas valve. | Electrical fault between PCB and valve (coils shorted/grounded or valve jammed); check wiring/insulation, control voltages, and coil resistance. If the valve does not respond or is shorted, replace it. |
| F62 | Delay in the closing of the gas valve. | The valve does not close in time or loses tightness, causing a delay in flame extinction; check closing times and gas leaks, and replace the valve if it does not seal correctly. |