| F.26 | Fault: gas valve not functioning. | The ignition control board governs the stepper motor of the gas valve; if its control stage fails, the valve does not respond and the unit locks out. Verification: measure the control signal to the stepper motor during the ignition attempt; if there is no signal and the wiring/valve assembly are OK, the board is defective. |
| F.27 | Safety shutdown: incorrect flame detection. | Fault in the flame control electronics integrated in the PCB (ionisation), which simulates or fails to detect a flame. Verification: check ionisation current (≈2–8 μA) and grounding; if electrodes/wiring are correct and the issue persists, replace the PCB. |
| F.28 | Start-up fault: ignition failed. | If the ignition PCB does not excite the spark transformer or does not manage ionisation, the start-up fails despite having correct gas. Verification: check HV output to ignition transformer and ionisation signal; if they are missing and gas/electrodes are OK, the PCB is the cause. |
| F.61 | Gas valve control/activation fault. | The output stage of the PCB controls the valve; an electronic defect prevents its correct activation. Verification: measure the control voltage to the valve during ignition; if it is non-existent or erratic and the valve/wiring are correct, the PCB is faulty. |
| F.62 | Gas valve fault: disconnection delay. | The circuit of the PCB should cut off the gas valve when turning off; if the stage remains 'stuck' or delays the cut-off, F.62 appears. Verification: check that the gas valve loses power instantly at the end of the flame; if not and the valve is not jammed, the PCB is the cause. |
| F.67 | Fault: electronics/flame (flame signal not plausible). | The electronic processing of the ionisation signal on the PCB returns incoherent values, causing a lockout. Verification: rule out ionisation/electrodes/ground, and if the implausible reading persists, replace the ignition control board. |
