PCB Junkers Eurosmart ZWA24 (1AM/1KM) Ref. 8748300561
If your boiler does not start, locks out, or exhibits erratic behavior, you may need the Junkers Eurosmart ZWA24 (1AM/1KM) PCB (control board) Ref. 8748300561. This board controls the ignition, burner modulation, pump, and safety features of the boiler. When it fails, you may notice that the reset button blinks at 1 Hz, indicating a lockout due to ignition failure or overheating. It is compatible with several models in the Junkers Eurosmart range, such as ZWA 24-1 AM 23 and ZWA 24-1 KM 23, among others. It is recommended to replace it upon detecting these symptoms to avoid further issues.
VAT included
Consult via WhatsAppJunkers boilers compatible with reference 8748300561
PCB with reference 8748300561. Six confirmed compatibilities: ZWA 24-1 AM 23 and ZWA 24-1 KM 23.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Junkers ZWA 24-1 AM 23 | Junkers Eurosmart ZWA 24-1 | Contrasted |
| Junkers ZWA 24-1 KM 23 | Junkers Eurosmart ZWA 24-1 | Contrasted |
| Junkers ZWA 24-1 AM 31 | Junkers Eurosmart ZWA 24-1 | Contrasted |
| Junkers ZWA 24-1 KM 31 | Junkers Eurosmart ZWA 24-1 | Contrasted |
| Junkers ZWA 24-1 A 23 | Junkers Eurosmart ZWA 24-1 | Contrasted |
| Junkers ZWA 28-1 AM 23 | Junkers Eurosmart ZWA 28-1 | 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 ref. 8748300561 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 8748300561. 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 8748300561 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 shows no signs of life: no display, no ignition spark, no fan.
Cause: A total failure in the power supply or in the microcontroller of the PCB renders the entire system inoperable.
First, check the main fuse of the house and the thermal switch of the boiler before declaring the PCB as faulty.
- 02
A different lock code appears each time an attempt is made to reset, with no apparent relationship between them.
Cause: The PCB generates inconsistent readings due to an internal fault, not because each indicated component is actually faulty.
Repeat the reset two or three times and note if the code changes each time; if so, focus more on the PCB than on the components indicated.
- 03
The boiler ignites, but the flame appears unstable or fluctuates without any change in the heating demand.
Cause: The PCB does not maintain a stable control signal sent to the modulating gas valve.
Check the gas inlet pressure and the cleanliness of the burner first; rule out those points before looking at the PCB.
- 04
The fault indicator is flashing with a pattern that does not match any code in the manual.
Cause: A fault in the microcontroller of the PCB causes flickering that does not correspond to any actual fault code.
Count the blinks twice in a row to confirm that the pattern is real and not a false reading before assuming a fault in the PCB.
Fault codes from Junkers that this part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| The reset button flashes at 1 Hz (once per second) | Fault indicator: lockout due to ignition failure/overheating/internal fault. | A defective PCB can cause this condition by failing in flame control, power supply, or signal management; check by following Test D in the manual (voltages at ST20/ST2, wiring/ionisation control) and, if all peripherals are correct, replace the PCB. |
| The reset button flashes at 4 Hz (four times per second) | Safety/evacuation lockout (pressure switch/NTC/fan/encoder connector). | If the PCB does not power/read the pressure switch, NTC, or the encoder connector correctly, the unit enters 4 Hz; check according to Test E (encoder connector, NTC/pressure switch inputs, continuity and 5 V) and, if the sensors/wiring are ruled out, 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 Junkers 8748300561 PCB.
- Catalogue reference
- 8748300561
- Brand
- Junkers
- Type of part
- PCBs (control boards)
- Units in stock
- 15 units
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- 1-2 business days
- 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.
- Part reference
- 8748300561
Frequently asked questions about the PCB 8748300561
Does this PCB fit a Junkers ZWA24-1KM31?
Does it also work for boilers ZWA28 or only for ZWA24?
How do I distinguish this PCB from other versions of the Eurosmart ZWA24?
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