Main PCB Saunier Duval Isofast 21 Condens F30 B 1 Ref. 0020066125
The Main PCB Saunier Duval Isofast 21 Condens F30 B 1 Ref. 0020066125 is a component that controls the ignition, burner modulation, pump, and safety features of the boiler. When it malfunctions, the boiler may fail to start, lock out, or exhibit erratic behavior, potentially displaying fault codes F.63, F.64, F.65, or F.67. This PCB is compatible with the Isofast 21 Condens F30 B/1 and Isofast 21 Condens F35 models, among others. It is recommended to replace it upon detecting these symptoms or fault codes.
Saunier Duval boilers compatible with reference 0020066125
PCB with reference 0020066125. Two confirmed compatibilities: Isofast 21 Condens F30 B/1 and Isofast 21 Condens F35.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval Isofast 21 Condens F30 B/1 | Isofast 21 Condens | Contrasted |
| Saunier Duval Isofast 21 Condens F35 | Isofast 21 Condens | 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. 0020066125 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 0020066125. If it is not visible, do not identify the part by 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 0020066125 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 is completely dead, neither the display nor any indicator lights up.
Cause: The control module is not receiving or distributing power to the rest of the boiler.
Check that the boiler is powered and that the accessible fuse is not blown before replacing the complete module.
- 02
A permanent lockout fault code appears that does not disappear with resets.
Cause: The PCB detects an out-of-range safety condition and does not release the ignition cycle.
Note the exact code; in this model, it's advisable to first rule out the sensor and water pressure, common causes of this same alert.
- 03
The pump or the burner do not start, even though a click can be heard inside the boiler when trying.
Cause: This PCB has two relays that switch the power supply to the pump and burner; if one fails, the click does not close the circuit.
Listen if the clicking repeats without the component starting: it's the typical sign of a relay that has stopped making good contact.
- 04
The module makes a relay clicking noise repeatedly without the boiler starting up.
Cause: The relay activates and deactivates in a loop because it does not receive confirmation that the component has started correctly.
Check first that the pump rotates freely and that the burner is not stuck: if the relay switches in a loop, it is advisable to rule out those parts first.
Fault codes from Saunier Duval that this spare part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| F.63 | EEPROM fault | The EEPROM of the main PCB is corrupted/unreadable; if sensors and wiring are OK, the fault is with the PCB. Check power supply and connectors; if the issue persists, replace the PCB. |
| F.64 | Electronic fault / NTC | Measurement circuit fault in the PCB (ADC/NTC reading). With NTC and harness correct, check grounds/signals on the board; if the error persists, replace the PCB. |
| F.65 | Fault: PCB temperature | The electronics of the PCB exceed its internal safety temperature or the internal sensor of the PCB fails. Check external causes (heat, ventilation) and, if the reading is incorrect or the fault persists, replace the PCB. |
| F.67 | Fault: electronics/flame | Defective flame signal processing in the PCB. If the ionisation electrode/cable and ventilation are fine and the "signal not plausible" persists, the cause is the control board; check grounds/signals and replace it if necessary. |
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 PCB 0020066125
- Catalogue reference
- 0020066125
- Brand
- Saunier Duval
- Type of part
- PCBs (control boards)
- Units in stock
- 0 units
- 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.
- Printed code (barcode)
- 0020066125
- Brand of the relays
- ZETTLER (two orange relays on the PCB)
- Zettler relay model
- AZ969-1CE-24DC(S), 6A 250VAC/30VDC, date 0313
Manuals and technical documentation
Official documentation of the boiler, useful for locating the part and cross-referencing the fault codes.
- Saunier Duval Isofast 21 Condens F30 B/1 Manual (PDF)Document © Saunier Duval, provided as a technical reference.
Frequently asked questions about the PCB 0020066125
What code do I need to check on the label of my Isofast 21 Condens F30?
Does this PCB also work for the Isofast 21 Condens F35?
Is it the main PCB or a secondary PCB of the Isofast 21 Condens?
When should this PCB be replaced in the Isofast 21 Condens F30/F35?
