| F.26 | Fault: gas valve not functioning. | The Honeywell gas valve S1071400 does not open because the stepper motor/solenoids do not receive or do not respond to the command. Check the connector/harness, coil continuity, and ensure that the valve is powered during the ignition attempt; also check that there is no pressure at the outlet during the attempt. |
| F.27 | Safety shutdown: flame simulation. | Defective/leaky gas valve S1071400 allows gas to pass when it should be closed, simulating a flame. Check tightness and closure: perform a pressure drop test at the burner inlet and confirm that ionisation ceases when the gas is cut off. |
| F.28 | Start-up fault: ignition failed. | The gas valve S1071400 does not open or is poorly calibrated, preventing the gas supply during ignition. Check that the electronics command opening (voltage to coils) and that pressure appears at the outlet during the attempt; if it does not open or is erratic, replace/adjust. |
| F.61 | Fault: gas valve control. | Electrical defect in valve S1071400 (coil short-circuited/grounded) or in its wiring causes activation fault. Check coil resistance/insulation and continuity of the harness to the PCB; if there is a ground leak or values are out of range, replace the valve. |
| F.62 | Gas valve fault. Disconnection delay. | The S1071400 valve takes time to close or remains unsealed, maintaining gas after the stop command. Check closing time and tightness (pressure/ionisation test after cut-off); if gas or residual flame persists, replace the valve. |
