Junkers Cerastarcomfort ZWN 25 8 MFA PCB Ref. 8748300933
The Junkers Cerastarcomfort ZWN 25 8 MFA PCB, with reference 8748300933, is the brain of the boiler, responsible for controlling the ignition, burner modulation, pump, and various safety features. When it fails, the user may notice that the boiler does not start, locks out, or exhibits erratic behavior, potentially displaying fault codes such as F0 or F7. This PCB is compatible with models such as the ZWN 25-8 MFA and ZWN 30-8 MFA, among others in the Cerastar Comfort range. It should be replaced when these symptoms of malfunction occur.
VAT included
Consult via WhatsAppBosch Junkers boilers compatible with reference 8748300933
PCB with reference 8748300933. 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 ZWN | Contrasted |
| Bosch Junkers ZWN 30-8 MFA | Cerastar Comfort ZWN | 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. 8748300933 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 8748300933. 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 8748300933 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 off: there is no pilot light or indicator on.
Cause: The PCB manages all the internal power supply, and if its startup stage fails, the boiler shows no signs of life.
Check that power is reaching the boiler and that the fuse on the PCB is not blown before replacing it.
- 02
Random lockouts occur at different times and without any clear pattern.
Cause: An intermittent fault in the PCB can cause erroneous readings from the sensors at specific times, unrelated to usage.
Keep a record of when each blockage occurs (time, whether there is domestic hot water or heating running) before changing the PCB.
- 03
The display or the indicator lights flash intermittently, sometimes without an apparent reason.
Cause: The circuit on the PCB that powers the display can progressively fail before it stops working completely.
Check that the mains voltage is stable in that area of the installation before replacing the PCB.
- 04
The circulation pump does not start even though the system is requesting heating.
Cause: The PCB sends the electrical command to the pump; if that output fails, the pump does not receive power even if everything else is working.
Check with a multimeter if there is voltage reaching the pump when there is demand, before assuming that the PCB is the culprit.
Fault codes for Bosch Junkers that this part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| F0 | Internal fault. | Fault in the PCB/Heatronic (PCB). After checking electrical contacts and ignition cables and resetting, if the error persists, it is confirmed by replacing the PCB (or bus module if applicable). |
| F7 | Even though the appliance is turned off, a flame is detected. | Humidity or defect in the PCB causes a false ionisation signal; check by drying/inspecting the PCB and, if it persists or there is damage, replace the board. |
| b1 | Coded connector not detected. | The control board does not recognise the encoder; check connector/wiring. If the encoder is correct, the cause is the PCB (reading/input on PCB). |
| b2 | Internal data error. | Data corruption in electronics (Heatronic/EEPROM). Try resetting to factory settings (function 8.E); if it reappears, the PCB is faulty and should be replaced. |
| b3 | Internal data error. | Same origin as b2 (internal data on the PCB). After resetting to factory settings, if it persists, it confirms a fault in the printed circuit and it should be replaced. |
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 8748300933
- Catalogue reference
- 8748300933
- Brand
- Bosch Junkers
- Type of part
- PCBs (control boards)
- Units in stock
- 11 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- Delivery time shown at checkout
- Return
- 14 days
Frequently asked questions about the PCB 8748300933
Is this PCB suitable for my Junkers ZWN 30/8 MFA boiler?
Spare parts related to Bosch Junkers Cerastar Comfort ZWN
