PCB Junkers (Bosch Thermotechnology) ZWA 24-1 AM23 - Ref. 8748300246
If your boiler does not start, locks out, or exhibits erratic behavior, a technical diagnosis must confirm whether you need the Junkers (Bosch Termotecnia) PCB (control board) ZWA 24-1 AM23 - Ref. 8748300246. This control board manages the ignition, burner modulation, pump, and safety features of the boiler. When it fails, you will notice that the reset button flashes at 1 Hz, indicating a lockout due to ignition failure, or at 4 Hz, signaling a safety lockout. It is compatible with models such as ZWA 24-1 AM 23, ZWA 24-1 KM 23, among others. A technician must confirm through diagnosis whether it needs to be replaced when these symptoms are present or when a malfunction is detected.
Bosch Junkers 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 |
|---|---|---|
| Bosch Junkers ZWA 24-1 AM 23 | Junkers Eurosmart ZWA 24-1 | Contrasted |
| Bosch Junkers ZWA 24-1 KM 23 | Junkers Eurosmart ZWA 24-1 | Contrasted |
| Bosch Junkers ZWA 24-1 AM 31 | Junkers Eurosmart ZWA 24-1 | Contrasted |
| Bosch Junkers ZWA 24-1 KM 31 | Junkers Eurosmart ZWA 24-1 | Contrasted |
| Bosch Junkers ZWA 24-1 A 23 | Junkers Eurosmart ZWA 24-1 | Contrasted |
| Bosch 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
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 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 that require diagnosis on the PCB 8748300561
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, makes no noise, and the display is off.
Cause: The PCB is not receiving power or is not processing the supply, so it cannot start.
Check the fuse on the PCB and verify that the main switch and the differential switch in the house are in the correct position.
- 02
A fixed fault code appears on the screen and the boiler does not start even after you reset it.
Cause: The control electronics detect an incorrect signal in its circuits and block operation for safety reasons.
Make sure to note the exact code before purchasing, as it may indicate a specific component (sensor) instead of the complete PCB.
- 03
The thermostat or the remote control are not responding, although the boiler seems to be on.
Cause: The microprocessor on the PCB does not process the commands from the connected devices.
Cut the power for one minute, reconnect it, and check that the wiring of the control is properly secured in its terminal block before ruling out the PCB.
- 04
The boiler turns off by itself intermittently, without a clear pattern.
Cause: A fault in the PCB causes signal interruptions that the control unit interprets as a shutdown command.
Open the cover and check for signs of moisture, burnt components, or poorly fitted connectors on the PCB.
Bosch Junkers fault codes that require diagnosis
| Code | Fault | Technical checks |
|---|---|---|
| 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 Bosch Junkers PCB 8748300561
- Catalogue reference
- 8748300561
- Uniclima internal SKU
- PLBO073
- 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
Part data and available documentation
Contrast the label codes, PCB, and revision with the installed part; they are not necessarily equivalent references.
- Component manufacturer
- Junkers (Bosch Termotechnology)
- Reference
- 8748300246
- PCB code engraved on the copper
- 8748301190 (the last two digits are uncertain: they could be 190/110/119)
- The reference that was published in the catalog until now (8748300561) is incorrect; the correct reference is 8748300246.
Frequently asked questions about the PCB 8748300561
Does this PCB fit a Junkers ZWA 28-1 AM23?
Does the code engraved on the copper of the PCB of the ZWA 24-1 serve to order the spare part?
Does this PCB work for a Junkers ZWA 24-1 KM31?
Spare parts related to Bosch Junkers Junkers Eurosmart ZWA 24-1
