Saunier Duval Isofast F 28 E Ignition PCB Ref. 05707900
The ignition PCB controls the startup, burner modulation, pump, and safety features of the boiler. When it fails, the boiler may not start, lock out, or operate erratically, displaying fault code 04: ignition failure, as the flame is not detected. This component is compatible with boilers from the Isofast range, such as the Isofast C 28 E and F 28 E, among others, as well as with models from Isomax and Themis. A technician should confirm through diagnosis whether it needs to be replaced if you experience ignition problems or unstable operation.
- Type of part
- PCBs (control boards)
- Status
- Refurbished
- Catalogue reference
- 05707900
- Warranty
- 1 year
Saunier Duval boilers compatible with reference 05707900
PCB with reference 05707900. Seven confirmed compatibilities: Isofast C 28 E and Isofast F 28 E.
Verified compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval Isofast C 28 E | Isofast | Verified |
| Saunier Duval Isofast F 28 E | Isofast | Verified |
| Saunier Duval Isofast C 35 E | Isofast | Verified |
| Saunier Duval Isofast F 35 E | Isofast | Verified |
| Saunier Duval Isomax C 28 E | Isomax | Verified |
| Saunier Duval Isomax F 28 E | Isomax | Verified |
| Saunier Duval Themis 23 mE | Themis | Verified |
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 ref. 05707900 is the part for your boiler
The part reference, model, and equipment revision must be verified against the manufacturer's documentation.
- Find the reference printed on the installed part and check whether it matches the catalogue reference 05707900. 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 that require diagnosis on the PCB 05707900
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 burner does not ignite even though the main PCB seems to be functioning normally.
Cause: This auxiliary PCB generates the ignition spark; if it fails, the burner will not ignite even if the rest is functioning.
Make sure that the connector between the main PCB and this auxiliary PCB is properly fitted before replacing it.
- 02
The ignition fault appears intermittently, sometimes it ignites and sometimes it does not.
Cause: A component of the auxiliary PCB that partially fails generates a weak or inconsistent spark depending on the operating temperature.
Note whether the fault is more frequent when cold or after several hours of use to differentiate a thermal fault from one related to the electrode.
- 03
A flame error appears on the boiler display even though gas is reaching the burner properly.
Cause: Without a spark from this auxiliary PCB, there is no flame ionization to detect, and the control unit interprets that there is no combustion.
Check the ignition electrode and its wiring before declaring the auxiliary PCB defective, as both share the same symptom.
- 04
The ignition attempt can be heard, but the burner does not ignite.
Cause: The auxiliary PCB works together with the main one during the startup; if it fails, the ignition cycle is interrupted without combustion.
Check the gas pressure and ensure that the gas valve opens correctly, to rule out that the fault is not with this auxiliary PCB.
Fault codes Saunier Duval that require diagnosis
| Code | Fault | Technical checks |
|---|---|---|
| 04 | Ignition fault: flame not detected. | The ignition module/spark generator (allumeur) may not deliver high voltage to the electrode or may fail intermittently, preventing the spark and causing the 04. Check by observing if there is a spark at the electrode and inspecting the wiring/connections of the allumeur; if there is no spark with correct gas and polarity, replace the module. |
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 05707900 PCB.
- Catalogue reference
- 05707900
- Uniclima internal SKU
- PLCAAUXISOFASTF28E
- Brand
- Saunier Duval
- Type of part
- PCBs (control boards)
- Units in stock
- 5 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- Delivery time shown at checkout
- Return
- 14 days
Part data and available documentation
Contrast the label codes, PCB, and revision with the installed part; they are not necessarily equivalent references.
- voltage
- 12V
Frequently asked questions about the PCB 05707900
Is this ignition auxiliary board the main board of the Saunier Duval Isofast F 28 E?
Is this PCB Ref. 05707900 compatible with the Saunier Duval Isomax F 28 E?
What function does this auxiliary PCB serve in the startup of the Isofast F 28 E?
How many models are compatible with this auxiliary ignition PCB?
What fault code is documented for this PCB?
What is the reference for this ignition auxiliary PCB?
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