| F.26 | Fault: gas valve not functioning. | The stepper motor/coils of the valve do not operate or are disconnected, so it does not open/modulate. Check the continuity of the coils, connector, and harness up to the PCB and ensure it receives voltage in test P.0. |
| F.27 | Safety shutdown: incorrect flame detection. | The sealed gas solenoid valve may allow gas to pass when it should be closed, causing an implausible flame signal. Check the valve's tightness/closure and absence of flame with the gas cut off. |
| F.28 | Start-up fault: ignition failed. | Among the causes is an incorrect/faulty gas valve that does not open or supply flow. Check inlet pressure, that the valve is the correct reference, activation signal, and pressure/output during the ignition attempt. |
| F.56 | Fault in the regulation of the circulating flow sensor. | The manual associates this fault with a faulty gas valve or its wiring harness, so a defective valve may cause incorrect flow/mix reading/regulation. Check the valve and wiring; if it reappears after adjustment, replace the valve. |
| F.61 | Gas valve control fault. | The PCB detects that it cannot activate the valve (coils grounded/cut). Check insulation and resistance of coils, continuity of the harness, and control output from the electronics. |
| F.62 | Gas valve fault. Disconnection delay. | The valve sticks or leaks and takes time to close after the flame extinguishes. Check that the flame signal drops when the gas is cut and the valve's tightness/quick closure; replace if there is a delay/leak. |
