| F.42 | Resistance fault coded (probably in combination with F.70). | The gas type coding resistor located on the PCB (SD623) may be open/short-circuited or poorly read. Check the continuity/value of the resistor on the PCB and, after replacing the board, adjust/confirm the DSN and product coding in the service menu. |
| F.61 | Fault in the activation of the gas valve. | The driver/output of the PCB (SD623) that excites the gas valve may fail or short-circuit to ground. Check that the PCB delivers the correct voltage to the EV during demand and rule out coils/wiring before attributing it to the PCB. |
| F.62 | Fault in the gas valve disconnection delay. | The PCB (SD623) may not cut off the power to the EV in time or may misinterpret the flame shutdown. Check that the EV drops to 0 V when stopping and that there is no undue delay from the command; if the valve/wiring are fine, the fault is with the PCB. |
| F.63 | Fault: EEPROM. | Internal memory of the SD623 PCB is corrupted/defective. Attempt reset and fault clearing; if it reappears, check power supply/electrical noise and replace the PCB. |
| F.64 | Fault in the electronics / NTC. | The reading circuitry/ADC on the SD623 board can give erroneous readings even if the NTCs are fine. Check the ohms of the NTC and the continuity of the wiring; if they are correct, the origin is the PCB. |
| F.65 | Fault: PCB temperature. | Actual overheating of the SD623 or fault of the thermal sensor integrated in the PCB. Check ventilation and actual temperature; if it is normal and the error persists, the PCB is defective. |
| F.67 | Fault: electronics/flame. | The flame control of the SD623 does not correctly process the ionisation signal. Measure ionisation current and ground continuity; if the signal is correct and the fault persists, the PCB is the cause. |
| F.70 | Invalid product code (DSN). | After simultaneously replacing the display and SD623 PCB, the DSN was not reconfigured or the coding resistor does not match. Verify/adjust the product code at the service centre and check the coding resistor/associated wiring. |
