| F.61 | Fuel valve control fault | The PCB does not correctly control the gas valve (power/output stage or faulty return reading). Check voltage and continuity between the PCB and the valve during demand; if wiring/valve are OK, the cause is the PCB. |
| F.62 | Fuel valve disconnection delay fault | The control circuit of the PCB does not cut the power supply to the gas valve within the expected time or interprets the flame extinction late. Check if there is voltage remaining at the valve connector after shutdown and rule out a valve leak/fault; if it persists, the PCB is defective. |
| F.63 | EEPROM fault | Memory/parameterization error in the boiler's electronics (PCB). If the fault persists after a reset and the power supply is stable, the documented action is to replace the board. |
| F.64 | Electronic fault / NTC | The PCB (ADC/analog input) delivers implausible readings from sensors even though the NTC and wiring are fine. Verify sensors and continuity; if the readings are correct but the fault persists, the cause is the PCB. |
| F.65 | Fault: PCB temperature | Overheating of the electronics: the internal sensor of the PCB detects temperature out of range or the board overheats. Check for external causes (ventilation/heat sources) and, if it reappears without an external cause, replace the PCB. |
| F.70 | Invalid appliance code (DSN) | Unconfigured or misaligned PCB with the display after replacement (incorrect/absent DSN). Verify/adjust the DSN in the service menu (e.g., D93) according to the model; if it does not allow parameterization, reprogram or replace the PCB/display according to the manual. |
