Saunier Duval PCB SD623 Ref. 051687
When you open the hot water tap, the Saunier Duval SD623 PCB (Ref. 051687) is responsible for controlling the ignition and modulation of the burner, as well as the pump and the safety features of the boiler. If this part fails, you will notice that the boiler does not start, gets locked, or operates erratically, with faults such as F.42 or F.61 possibly appearing. It is compatible with the Saunier Duval SD623E boiler, among others. It is recommended to replace it when these malfunction symptoms are present.
VAT included
Consult via WhatsAppSaunier Duval boilers compatible with reference 051687
PCB with reference 051687. A proven compatibility: SD623E.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval SD623E | SD623E | Contrasted |
Can't see your model or have questions? The printed reference takes precedence. How to check it · Send us a photo via WhatsApp.
How to check if the reference 051687 is the part for your boiler.
What determines it is not the boiler model, but the reference printed on the part you already have installed.
- Find the reference printed on the installed part and check whether it matches the catalogue reference 051687. If it is not visible, do not identify the part from its shape alone.
- Check the full boiler model on its data plate and look for it in the model associations on this page.
- Compare the connections and physical body with the original part before installation.
- If anything is unclear, send us a photo of the marking via WhatsApp before placing your order.
Symptoms and faults that the PCB 051687 resolves.
The PCB controls the ignition, modulation, and safety features of the boiler. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The boiler does not ignite and the display is off.
Cause: The transformer on the PCB is not supplying the 24V necessary for the boiler to operate.
Measure the output voltage of the transformer (it should read around 24V); if it shows nothing, check the 220V input wiring before considering that the PCB is damaged.
- 02
The pump, the fan, or the gas valve are not working even though the boiler is trying to ignite.
Cause: The relays on the PCB are responsible for sending current to these components; if one of them fails, the corresponding component will not receive voltage.
Listen for the relays clicking when requesting ignition; if one does not sound while the other does, the problem lies with that relay.
- 03
The boiler ignites irregularly, sometimes it works and sometimes it doesn't.
Cause: A worn relay or a temporary fault in the electrical control of the PCB can cause inconsistent responses.
Try to turn on the boiler several times in a row and observe if it fails at the same moment in the sequence; a recurring fault at the same step can help identify the faulty component.
Fault codes from Saunier Duval that this spare part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| 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. |
These symptoms can have more than one cause. If your boiler displays a fault code, send it to us via WhatsApp along with a photo of the labeling, and we'll tell you if this is the part.
Data sheet for the Saunier Duval 051687 PCB.
- Catalogue reference
- 051687
- Brand
- Saunier Duval
- Type of part
- PCBs (control boards)
- Units in stock
- 1 unit
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- Delivery time shown at checkout
- Return
- 14 days
Data read on the part and in the manufacturer's documentation
What we have not been able to verify does not appear here.
- Primary transformer voltage
- 220V 50Hz
- Secondary transformer voltage
- 24V 13VA
- Thermal fuse transformer
- 80mA T, class T50/E
- PCB fuse
- 80mAT
- Relay (REL1 and REL2)
- Schrack RP420024, 24V=, 8A/250V~AC1, Made in Austria
- Condenser C8
- 400µF -250V- HP T
Frequently asked questions about the PCB 051687
Does Saunier Duval manufacture this PCB for the SD623E?
What relays does the Saunier Duval SD623E PCB have and where are they from?
When should this PCB of the SD623E be replaced?
What transformer is installed on the Saunier Duval SD623E PCB?
Spare parts related to Saunier Duval SD623E
