PCB Junkers Bosch ZWN 25 8 MFA 31 Ref. 8748300744
If your boiler does not start, locks out, or behaves erratically, you may need the Junkers Bosch ZWN 25 8 MFA 31 PCB, reference 8748300744. This control board is responsible for managing the ignition, burner modulation, pump, and safety features of the boiler. When it fails, fault codes F0, related to an internal fault, or A8, indicating a communication interruption, may appear. It is compatible with models such as the ZWN 25-8 MFA and ZWN 30-8 MFA from the Cerastar Comfort range, among others. It is recommended to replace it when problems are detected in the starting or operation of the boiler.
VAT included
Consult via WhatsAppBosch Junkers boilers compatible with reference 8748300744
PCB with reference 8748300744. Two confirmed compatibilities: ZWN 25-8 MFA and ZWN 30-8 MFA.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Bosch Junkers ZWN 25-8 MFA | Cerastar Comfort (CerastarComfort) | Contrasted |
| Bosch Junkers ZWN 30-8 MFA | Cerastar Comfort (CerastarComfort) | 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 8748300744 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 8748300744. 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 8748300744 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 turn on, not even the display: there are no signs of life.
Cause: The PCB is not receiving power because its power supply stage is faulty.
Check the fuse on the PCB and ensure that there is voltage at the main connector before replacing it.
- 02
The display shows a fault code and the boiler does not ignite the flame.
Cause: The control electronics detect an anomaly in the ignition sequence and block it for safety reasons.
Note the exact code and first rule out an external sensor (NTC, pressure switch, sensor) before replacing the PCB.
- 03
The buttons are unresponsive or the clock has stopped at a fixed time.
Cause: The microcontroller on the PCB has stopped processing the commands from the panel.
Cut the power for a couple of minutes to force a reset before declaring the PCB faulty.
- 04
The boiler turns off by itself halfway through a heating or domestic hot water cycle.
Cause: An internal relay on the PCB is intermittently losing contact.
Check that the connectors on the PCB are properly fitted and free of oxidation before replacing it.
Fault codes for Bosch Junkers that this part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| F0 | Internal fault/PCB fault. | Internal fault of the Heatronic PCB (memory, power supply, or control electronics) triggers the self-diagnosis; check voltage, fuses, and connectors, and if there is moisture in the electronic box; if it persists after reset and checks, replace the PCB. |
| A8 | BUS communication interrupted between the controller and the boiler electronics. | The BUS/CAN interface of the PCB (or its tracks/fuse) may fail and cut off communication with the controller; first check the wiring/controller and, if they are correct, measure the EMS/BB signal and inspect the PCB; if the issue persists, replace the PCB. |
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 Bosch Junkers PCB 8748300744
- Catalogue reference
- 8748300744
- Brand
- Bosch Junkers
- 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
Frequently asked questions about the PCB 8748300744
Does this PCB 8748300744 work for my Bosch ZWN25-8MFA 23 boiler?
What does the "2/2" marking next to a connector on the PCB 8748300744 mean?
Does the same PCB 8748300744 work for both the Bosch ZWN25-8MFA and the Junkers ZWN25-8MFA?
Spare parts related to Bosch Junkers Cerastar Comfort (CerastarComfort)
