Gas Mechanism G20 Saunier Duval Isofast F 35 E1 Ref. 05742800
When you turn on the hot water tap or activate the heating, the G20 gas mechanism of the Saunier Duval Isofast F 35 E1 is triggered to regulate the flow of gas to the burner. This gas valve is responsible for ensuring that the fuel reaches correctly, following the commands of the control board. If it fails, you will notice that the boiler does not ignite, there may be flame lockouts or modulation issues. This mechanism is compatible with models such as Isofast C 24 E V1, Isofast C 28 E1, among others. It is recommended to replace it if you experience faults such as F.26, F.27, F.28, F.61, or F.62.
VAT included
Consult via WhatsAppSaunier Duval boilers compatible with reference 05742800
Gas valve with reference 05742800. 15 confirmed compatibilities: Isofast C 24 E V1 and Isofast C 28 E1.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval Isofast C 24 E V1 | Isofast | Contrasted |
| Saunier Duval Isofast C 28 E1 | Isofast | Contrasted |
| Saunier Duval Isofast C 28 E1 NOx | Isofast | Contrasted |
| Saunier Duval Isofast C 35 E1 | Isofast | Contrasted |
| Saunier Duval Isofast F 28 E1 | Isofast | Contrasted |
| Saunier Duval Isofast F 35 E1 | Isofast | Contrasted |
| Saunier Duval Isomax C 28 E2 | Isomax | Contrasted |
| Saunier Duval Isomax F 28 E2 | Isomax | Contrasted |
| Saunier Duval Isotwin C 24 E | Isotwin | Contrasted |
| Saunier Duval Isotwin C 24 EA | Isotwin | Contrasted |
| Saunier Duval Isotwin C 24 EV | Isotwin | Contrasted |
| Saunier Duval Isotwin C 24 EV A | Isotwin | Contrasted |
| Saunier Duval Isotwin F 24 E | Isotwin | Contrasted |
| Saunier Duval Isotwin F 24 E1 | Isotwin | Contrasted |
| Saunier Duval Isotwin F 24 EA | Isotwin | 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 part number 05742800 is the one 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 05742800. 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 gas valve 05742800 resolves.
The gas valve regulates and modulates the gas flow to the burner. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The boiler does not ignite and there is no sound of the gas valve attempting to open.
Cause: The electro-actuator does not receive the command or does not rotate to open the gas valve, so the gas never reaches the burner.
Check that the electro-valve receives 24 VDC at its connector before declaring it faulty.
- 02
The boiler locks out as soon as the ignition is attempted, with a flame fault.
Cause: If the operator does not open in time or gets stuck halfway, the control board does not detect a flame and shuts off for safety.
Listen for a small click or buzz from the electro operator when starting; if there is no sound, the problem may be earlier, in the power supply.
- 03
The boiler ignites but turns off by itself after a few seconds.
Cause: The electro-valve actuator may close the passage prematurely due to an internal fault in the stepper motor.
Check if the display shows a gas pressure or flue error before assuming it is the electro-valve.
- 04
The boiler is not heating and the display does not show any clear error.
Cause: An electro-valve that does not close completely also prevents ignition, although it does not always provide a specific fault code.
Reset the boiler and check if it attempts to ignite at least once; if it doesn't attempt at all, check the main power supply first.
Fault codes from Saunier Duval that this spare part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| F.26 | Fault: gas valve not functioning. | The stepper motor of the gas mechanism (valve ref. 05742800) is not operating or is disconnected. Check coil continuity and signal from the PCB; during demand, verify with a manometer that there is no pressure variation at the valve outlet. |
| F.27 | Safety shutdown: incorrect flame detection. | Non-sealed gas solenoid valve or one that does not close properly produces an incoherent flame signal. Check the valve's tightness (leaks) and ensure the flame extinguishes upon closing; replace the valve if it does not seal. |
| F.28 | Start-up fault: ignition failed. | The gas valve does not open or is misadjusted, preventing supply to the burner. Check that it receives command/voltage and coil continuity; measure inlet/outlet pressures during the ignition attempt. |
| F.61 | Gas valve activation fault. | Short circuit to ground in the harness or valve coils, or driver fault in the PCB prevents the valve from activating. Check insulation to ground, coil resistance, and control signal from the electronics. |
| F.62 | Gas valve fault: disconnection delay. | The valve closes late or does not seal (leaks), allowing gas to pass after the stop command. Check for the closing 'click', immediate drop in ionisation, and absence of gas/flame; perform a tightness test and replace if it does not close in time. |
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 gas valve Saunier Duval 05742800
- Catalogue reference
- 05742800
- Brand
- Saunier Duval
- Type of part
- Gas valves
- 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.
- Nominal voltage
- 24 VDC
- Power
- 6 VA
- IP protection rating
- IP 20
- Type of gas
- Natural gas
- Batch code/date
- 200G3
- Code printed on the label
- 116 675 6
Frequently asked questions about the gas valve 05742800
Does this gas valve electro-actuator work for the Isofast F 35 E1?
What is the difference between this part and the mechanism of the Isomax F 28 E2, which shares the Ref. 05742800?
What fault indicates that the gas valve actuator needs to be replaced in the Isofast F35 E1?
Is there an equivalent reference to 05742800 for this electro-operator?
What is the IP protection rating of the gas valve electro-actuator of the Isofast F 35 E1?
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