Bosch Control PCB for Junkers Eurosmart ZWA 24-1 AM - Ref. 8748300488
The Bosch Control PCB for Junkers Eurosmart ZWA 24-1 AM - Ref. 8748300488 regulates the ignition, burner modulation, pump, and safety features of the boiler. When it fails, the boiler may not start, become locked, or operate erratically. The user will notice symptoms such as the reset button flashing at 1 Hz, indicating a lockout due to ignition failure or overheating, or at 4 Hz, signaling a problem in the flue gas system. This PCB is compatible with models such as ZWA 24-1 AM 23, ZWA 24-1 AM 31, among others in the Junkers Eurosmart ZWA 24 range. A technician should confirm through diagnosis whether replacement is necessary when operational faults or recurring lockouts occur.
- Type of part
- PCBs (control boards)
- Status
- Refurbished
- Catalogue reference
- 8748300488
- Warranty
- 1 year
Junkers boilers compatible with reference 8748300488
PCB with reference 8748300488. Four confirmed compatibilities: ZWA 24-1 AM 23 and ZWA 24-1 AM 31.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Junkers ZWA 24-1 AM 23 | Junkers Eurosmart ZWA 24 | Contrasted |
| Junkers ZWA 24-1 AM 31 | Junkers Eurosmart ZWA 24 | Contrasted |
| Junkers ZWA 24-1 KM 23 | Junkers Eurosmart ZWA 24 | Contrasted |
| Junkers ZWA 24-1 KM 31 | Junkers Eurosmart ZWA 24 | 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. 8748300488 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 8748300488. 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 that require diagnosis on the PCB 8748300488
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 ignite and there are no lights or indications on the panel.
Cause: If the PCB does not distribute the power, the rest of the components will be left without current to start.
Check the fuse on the PCB and verify that stable mains voltage is present before replacing it.
- 02
It triggers a fault code as soon as it is turned on and the boiler locks out immediately.
Cause: The PCB performs a self-check when starting; if it detects a reading out of range, it blocks the cycle before supplying gas.
Note the exact code displayed and compare it with the fault code table before replacing the PCB, as it may indicate a specific sensor.
- 03
The hot water comes out in bursts of temperature, rising and falling for no reason.
Cause: The PCB regulates the modulation of the flame according to the water demand; if its control stage degrades, it loses accuracy.
First, rule out scale or dirt in the heat exchanger and the water flow before blaming the PCB.
- 04
The boiler restarts by itself from time to time, as if it briefly loses power.
Cause: An intermittent fault in the internal power supply of the PCB can cause micro-cuts that reset the system.
Check the network and ground connections on the boiler; a poor contact can also cause this same symptom.
Junkers fault codes that require diagnosis
| Code | Fault | Technical checks |
|---|---|---|
| The reset button flashes at 1 Hz (once per second) | Lockout due to ignition/overheating/internal fault group. | The control board (Eurotronic/PCB) may fail in ignition/flame management or in powering sensors/actuators, causing this blockage. Check 230 V at ST2, signals/outputs at ST16, and if peripherals and wiring are correct, replace the board. |
| The reset button flashes at 4 Hz (four times per second) | Lockout due to flue evacuation/safety group or associated sensors. | A defect in the control board can prevent the correct management/reading of the fan, pressure switch, NTC, or the encoder connector, triggering the 4 Hz. Check connectors ST16/ST1, power supply to the fan, and continuity of sensors; if everything is okay and it persists, the board is the probable cause. |
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 Junkers 8748300488 PCB.
- Catalogue reference
- 8748300488
- Uniclima internal SKU
- PLBO072
- Brand
- 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
Part data and available documentation
Contrast the label codes, PCB, and revision with the installed part; they are not necessarily equivalent references.
- Component manufacturer
- Bosch
- Silkscreen reference
- 8 748 300 4??
Frequently asked questions about the PCB 8748300488
Is it an original Bosch PCB for the Junkers Eurosmart ZWA 24-1 AM 23?
For which models of the Eurosmart ZWA 24 range is this Bosch PCB compatible?
What should I do if the code on my Bosch PCB does not exactly match 8748300488 on my boiler?
What fault codes are documented for this PCB?
What is the reference for this Bosch PCB?
Is this Bosch PCB compatible with other models of Junkers boilers?
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