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. A technician must confirm through diagnosis whether replacement is necessary when these malfunction symptoms occur.
- Type of part
- PCBs (control boards)
- Status
- Refurbished
- Catalogue reference
- 8748300933
- Warranty
- 1 year
Boilers Junkers compatible with reference 8748300933
PCB with reference 8748300933. Two confirmed compatibilities: ZWN 25-8 MFA and ZWN 30-8 MFA.
Verified compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Junkers ZWN 25-8 MFA | Cerastar Comfort ZWN | Verified |
| Junkers ZWN 30-8 MFA | Cerastar Comfort ZWN | Verified |
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
The part reference, model, and equipment revision must be verified against the manufacturer's documentation.
- 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 that require diagnosis on the PCB 8748300933
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.
Junkers fault codes that require diagnosis
| Code | Fault | Technical checks |
|---|---|---|
| F0 | Internal fault. | Fault of the printed circuit board/Heatronic (PCB). After checking electrical contacts and ignition cables and resetting, if the error persists, confirm the cause using the manufacturer's diagnostic procedure (or bus module if applicable). |
| F7 | Even though the appliance is turned off, a flame is detected. | This code requires technical diagnosis according to the model manual and its review. It does not confirm on its own that this part is faulty nor justifies its replacement. The causes and the exact reference must be verified before intervening. |
| 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. | This code requires technical diagnosis according to the model manual and its review. It does not confirm on its own that this part is faulty nor justifies its replacement. The causes and the exact reference must be verified before intervening. |
| b3 | Internal data error. | This code requires technical diagnosis according to the model manual and its review. It does not confirm on its own that this part is faulty nor justifies its replacement. The causes and the exact reference must be verified before intervening. |
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.
Technical sheet: Junkers 8748300933
- Catalogue reference
- 8748300933
- Uniclima internal SKU
- PLBO171
- Brand
- 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?
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