Pressure Sensor Saunier Duval Isofast F 35 E
The water pressure sensor measures the pressure of the circuit and sends the reading to the PCB of the Saunier Duval Isofast F 35 E boiler. When it fails, it can result in incorrect readings, leading to lockouts due to false low pressure. The user may notice symptoms such as fault code F9, which indicates a pressure detector failure, or fault codes F.73, F.74, and F.75, which are related to out-of-range signals. This sensor is compatible with several models in the Isofast range, such as C24EV, C28E, C35E, and F35E1, among others. It should be replaced when these symptoms or faults occur.
VAT included
Consult via WhatsAppSaunier Duval boilers compatible with reference S57205
Pressure sensor with reference S57205. 41 verified compatibilities: C24EV and C28E.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval C24EV | Isofast | Contrasted |
| Saunier Duval C28E | Isofast | Contrasted |
| Saunier Duval C28E1 | Isofast | Contrasted |
| Saunier Duval C35E | Isofast | Contrasted |
| Saunier Duval C35E1 | Isofast | Contrasted |
| Saunier Duval F24E | Isofast | Contrasted |
| Saunier Duval F28E | Isofast | Contrasted |
| Saunier Duval F28E1 | Isofast | Contrasted |
| Saunier Duval F35E | Isofast | Contrasted |
| Saunier Duval F35E1 | Isofast | Contrasted |
| Saunier Duval C28E | Isomax | Contrasted |
| Saunier Duval C28E2 | Isomax | Contrasted |
| Saunier Duval F28E | Isomax | Contrasted |
| Saunier Duval F28E2 | Isomax | Contrasted |
| Saunier Duval Condens F35E | Isomax | Contrasted |
| Saunier Duval C24E | Isotwin | Contrasted |
| Saunier Duval F24E | Isotwin | Contrasted |
| Saunier Duval F28E | Isotwin | Contrasted |
| Saunier Duval Condens F30-A | Isotwin | Contrasted |
| Saunier Duval C24E | Themaplus | Contrasted |
| Saunier Duval F24E | Themaplus | Contrasted |
| Saunier Duval F25E | Themaplus | Contrasted |
| Saunier Duval F30E | Themaplus | Contrasted |
| Saunier Duval C24E | Themafast | Contrasted |
| Saunier Duval F24E | Themafast | Contrasted |
| Saunier Duval Condens F24E | Themafast | Contrasted |
| Saunier Duval Condens F30E | Themafast | Contrasted |
| Saunier Duval F24E | Themaclassic | Contrasted |
| Saunier Duval F25E | Themaclassic | Contrasted |
| Saunier Duval C24E | Themaclassic | Contrasted |
| Saunier Duval FAS24E | Themaclassic | Contrasted |
| Saunier Duval FAS25E | Themaclassic | Contrasted |
| Saunier Duval F24E | Themacondens | Contrasted |
| Saunier Duval F25 | Themacondens | Contrasted |
| Saunier Duval FAS25 | Themacondens | Contrasted |
| Saunier Duval C18E | Thematek | Contrasted |
| Saunier Duval C24E | Thematek | Contrasted |
| Saunier Duval F24E | Thematek | Contrasted |
| Saunier Duval C24E | Thema | Contrasted |
| Saunier Duval Condens F25 | Thema | Contrasted |
| Saunier Duval Condens F25 | Semia | 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 ref. S57205 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 S57205. 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 pressure switch S57205 resolves.
The pressure sensor measures the water pressure for the electronics. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The pressure on the display is at zero or very low, even though the circuit is full and leak-free.
Cause: The sensor does not correctly translate the water pressure, sending an incorrect signal to the control board.
Before changing it, measure the pressure with an additional manometer to verify if it matches what is displayed.
- 02
The boiler turns off due to "lack of pressure" from time to time, without anyone having touched the filling or there being any puddles.
Cause: The sensor sends intermittent signals that cause incorrect low pressure readings to the control board.
Check the connector and the cable of the sensor for moisture or oxidation before replacing the part.
- 03
The pressure number on the display fluctuates on its own, as if it has a life of its own.
Cause: If the sensor fails, the conversion of water pressure to electrical signal becomes unstable, causing variations without any real reason.
Bleed the air from the radiators and the circuit, as trapped air can cause pressure fluctuations that may be mistaken for a fault in the sensor.
- 04
The boiler does not ignite and the fault code indicates a pressure problem, but the circuit is properly filled.
Cause: If the sensor sends an anomalous value, the control unit interprets that there is a lack of water and blocks the start for safety.
Note the exact code displayed by the boiler and compare it with the manual before assuming that the problem is with the sensor.
Fault codes from Saunier Duval that this spare part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| F9 | Water pressure sensor fault. | The S57205 sensor does not deliver a valid signal (loose connector, short circuit, or obstructed hydraulic connection) and the PCB does not 'see' pressure; check wiring and pressure reading in diagnostic/menu and verify that the signal changes when pressurizing. |
| F.73 | Water pressure sensor signal out of range (too low). | Interruption/short circuit of the sensor or ground in the cable; check power supply and sensor signal, continuity of the harness, and ensure the sensor port is not blocked. |
| F.74 | Water pressure sensor signal out of range (usually too high). | Short circuit at 5/24 V or internal fault of the sensor; measure the sensor output and check if it remains fixed at high; inspect wiring and clean the orifice, replacing the sensor if it does not recover. |
| F.75 | No increase in pressure detected when the pump starts (pressure sensor and/or pump). | The sensor does not detect the pressure 'spike' due to a faulty sensor or blocked intake (first rule out air/lack of water/pump); check the pressure reading during start-up in service mode and the continuity/power supply of the sensor. |
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 Saunier Duval pressure sensor S57205
- Catalogue reference
- S57205
- Brand
- Saunier Duval
- Type of part
- Pressure sensors
- Units in stock
- 4 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- 1-2 business days
- 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.
- Batch number
- 0601220... (the 'L' at the beginning of 'LOT' and the end of the number are out of frame)
- Label code
- ...1444/01 (prefix cut off by framing)
Manuals and technical documentation
Official documentation of the boiler, useful for locating the part and cross-referencing the fault codes.
- Saunier Duval Isofast C28E Manual (PDF)Document © Saunier Duval, provided as a technical reference.
Frequently asked questions about the pressure sensor S57205
Does this pressure switch work for the Isofast F 35 E?
What batch and code does the label of this collector, ref. S57205, retain?
Is this sensor compatible with the Isotwin F 24 E or the Thematek F 24 E?
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