| F.61 | Fault: gas valve operation. | The PCB cannot correctly operate the gas valve (coils in short circuit/ground or without signal), preventing its opening/modulation. Check the continuity of coils, wiring, and control signal to the valve during the ignition attempt. |
| F.62 | Gas valve disconnection delay. | The gas valve does not close in time or loses tightness, resulting in residual flow and/or delayed flame signal. Check the tightness of the assembly and closing times by measuring ionisation and pressure at the ports before/after the valve when stopping the burner. |
| F.28 | Start-up fault: ignition failed. | If the gas valve is faulty/stuck or improperly actuated, it does not supply gas to the burner despite the presence of a spark, resulting in no flame. Check the control voltage to the valve during the ignition attempt and the outlet pressure at the test point. |
| F.29 | The flame goes out during operation and the ignition retry fails. | A faulty or improperly adjusted gas valve can cause unstable flow/pressure and flame extinction under load. Check valve modulation, dynamic pressure in service, and adjustment with a combustion analyser. |
| F.27 | Safety shutdown: flame simulation. | Gas leaks or defective closure of the magnetic gas valve may allow gas to pass when it should be closed, resulting in an improper 'flame' detection. Check the valve's tightness and ensure that the ionisation signal drops to 0 when the gas is shut off. |
