Bosch PCB 8748300486 for Junkers ZWA 24 1KE23

Application to the exact variant pending confirmation. It is the PCB of the boiler. from a board of the series (8748300561), this type of board manages the ignition, modulation, safety features, and communication. Before suspecting it, check the power supply, fuses, and connectors.

Type of part: PCBs (control boards)
Status: Refurbished
internal SKU: PLC207
Warranty: 1 year

VAT included Stock · 4 units

Compatibility

Bosch (Junkers) compatible boilers

PCB. 0 verified compatibilities. There are 2 other models that we are still checking.

Models pending verification

These models are associated with this reference, but we have not finished verifying them yet, so we do not consider them compatibleIf your boiler is one of them, send us a photo of the part you are going to replace and we will verify it before you purchase.

Bosch (Junkers) Junkers Eurosmart ZWA 24-1	Bosch (Junkers)	Unconfirmed
Junkers ZWA 24 1KE23	Bosch (Junkers)	Unconfirmed

Can't see your model or have questions? The printed reference takes precedence. How to check it · Send us a photo via WhatsApp.

Guide

How to check if it is the part for your boiler

The part reference, model, and equipment revision must be verified against the manufacturer's documentation.

Look for the code 8 748300 on the printed circuit board in silkscreen and, handwritten next to it, the suffix 486: together they form 8748300486.
Compare the other marked ones: HT II-2a, the relays HT-2A and H1 II-2, and the fuses T1.25A (glass fuse holder) and T2A (ceramic).
Do not rely solely on the beginning 8 748 300: other boards in the series, such as 8 748 300 431 or 8 748 300 496, start the same way and are different codes.
Check the specification plate of your boiler to confirm that the model is ZWA 24 1KE23.
if they match, call us at 911 17 77 77 with the model of your boiler. Any questions? Send us a photo of the label of your part and the data plate of the boiler from Contact.

Diagnosis and fault codes

Symptoms that require diagnosis on the PCB

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 reset button flashes once per second.
Cause: Ignition fault, overheating, internal fault or leaks in the safety valve. Among the most common causes is the PCB.
Have a technician check it. Do not insist on repeated resets.
02
The reset button flashes four times per second.
Cause: Loose or defective encoder connector, or incorrectly installed or defective heating or domestic hot water NTC. The pressure switch, fan, or flue duct may also fail.
Have a technician check it, who will verify the sensors and the connector before replacing the PCB.
03
The heating is not working, but hot water is coming out.
Cause: Fault in the ambient thermostat signal or its connection. It may also be a faulty thermostat or the PCB.
Check the room thermostat and its cable. If it remains the same, have a technician check it.
04
The boiler is not working and the indicators are not lighting up.
Cause: No voltage: faulty fuse F1 or F2, faulty transformer or connection, or PCB.
Have a technician check it.
05
There is no hot water, but the heating works.
Cause: Faulty water flow detector (turbine) or faulty hot water NTC. It could also be the PCB.
Have a technician check it.
06
The heating is not working, but domestic hot water is coming out.
Cause: Incorrect signal from the room thermostat, or faulty room thermostat, or fault in the PCB.
Check the room thermostat and its wiring. If the heating still does not work, have a technician check it.

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 data

Technical sheet: Bosch (Junkers) PCB

Uniclima internal SKU: PLC207
Brand: Bosch (Junkers)
Type of part: PCBs (control boards)
Units in stock: 4 units
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.

Silkscreen next to the glass fuse holder: T1.25A
Silkscreen next to the ceramic fuse holder: T2A
Inventory — Subcomponent relay: H1 11-2A HT-2A H1 II-2; marked CA CA CA
Inventory — Application indicated in inventory: ZWA 24 1KE23
Printed PCB silkscreen: 8 748300
Handwritten suffix on PCB: 486
Identification — Marked code: 8 748 300
Identification — Marked code: HT II-2a
Identification — Marked code: CA CA CA
Serigrafia junto al portafusible de vidrio: T1.25A
Serigraphy next to the ceramic fuse holder: T2A
Inventory data — Subcomponent relay: H1 11-2A
Inventory data — Subcomponent relay: HT-2A
Inventory data — Subcomponent relay: H1 II-2; marked CA CA CA
Inventory data — Application indicated in inventory: ZWA 24 1KE23
Registered reference: 8748300486
Additional markings: PCB markings: silkscreen 8 748300 and handwritten suffix 486. Relays with readings H1 11-2A; HT-2A; H1 II-2; HT II-2a; code/legend CA CA CA. Fuses with readings T1.25 A and T2 A; silkscreen next to the ceramic fuse holder T2A.
Pending applications to verify: ZWA 24 1KE23 — compatibility noted; pending confirmation by variant.

Before purchasing

To confirm: Junkers Eurosmart ZWA 24-1 — 1 source: from a private individual, without specifying the variant.
Not compatible or excluded from the source: Junkers ZWA 24-1 K — Its official spare parts list (ed. 28.8.02) provides another PCB: 8 748 300 431. A manual from the series lists the K 23, with a name similar to 1KE23; it is not established that it is the same boiler.
Not compatible or excluded by default: Junkers ZWA 24-1 A — Its official spare parts list (ed. 28.8.02) provides another PCB: 8 748 300 496
Do not confuse: 8 748 300 431 — PCB from the official spare parts list of the ZWA 24-1 K (document 7 181 465 352) — Another code: ends in 431, not in 486.
Do not confuse: 8 748 300 496 — PCB from the official spare parts list of the ZWA 24-1 A (document 7 181 465 343) — Another code: ends in 496, not in 486.
Do not confuse: 8748300561 / 8748300488 — PCBs for the Eurosmart ZWA 24-1 AM and KM — Other codes. From what we could read, without additional confirmation, they are linked to 8748300486.
To confirm: The markings are read on the part itself. External (2023) names 8748300486, without specifying a variant; the official series lists provide other PCBs.
Compatibility with the ZWA 24 1KE23 registered. A single external source (Italian, possible copy of) names the 8748300486, without variant; the official lists from A and K provide other PCBs.
Pending registered applications to confirm by model, variant, or programming: Junkers ZWA 24 1KE23.

Frequently Asked Questions

Frequently asked questions about the PCB (control board)

How do I identify the Bosch PCB 8748300486?

On the printed circuit board, 8 748300 is printed, and handwritten next to it is the suffix 486: together they make 8748300486 (8 748 300 486 in Bosch format). Also compare HT II-2a, the relays HT-2A and H1 II-2, and the screen-printed fuses: T1.25A next to the glass fuse holder and T2A next to the ceramic one.

Is it compatible with my Junkers ZWA 24 1KE23?

The compatibility of this variant is pending confirmation. Registered: for the Junkers ZWA 24 1KE23. (Italian) from 8748300486 for the Eurosmart ZWA 24-1 family without mentioning the 1KE23 variant, so the confirmation is from the workshop. Check the model on the rating plate of your boiler.

What if my boiler is a ZWA 24-1 K, ZWA 24-1 A, or ZWA 24-1 AM/KM?

The compatibility of this variant is pending confirmation. We do not consider it valid without verification. The official spare parts lists for the ZWA 24-1 K and ZWA 24-1 A (ed. 28.8.02) provide different PCBs: 8 748 300 431 and 8 748 300 496. A manual from the series lists the ZWA 24-1 K 23, with a name similar to 1KE23: it is not established that it is the same boiler. The 8748300561 is for the ZWA 24-1 AM and KM. Send us a photo of your PCB label and boiler from Contact, or call us at 911 17 77 77.

Is 8748300486 the same as 8748300561 or 8748300488?

We don't know. The 8748300561 / 8748300488 for the ZWA 24-1 AM and KM, and the Italian ones list the 8748300488 as the previous code for the 8748300561. In the text we were able to read from those pages, the 8748300486 does not appear, so we cannot say that it is equivalent or interchangeable: do not swap them without verifying.

What do 8 748 300, the handwritten 486, and HT II-2a mean?

8 748300 is the code printed on the circuit and the handwritten 486 completes it: 8748300486. The 8 748 300 alone is not enough: the official lists show other PCBs that start the same (431 in the ZWA 24-1 K, 496 in the ZWA 24-1 A). HT II-2a, HT-2A, and H1 II-2 are markings on the board and its relays; without additional confirmation, they explain it, use them only for comparison.

What fuses does it use and what are their values?

Our unit is printed with T1.25A next to the glass fuse holder and T2A next to the ceramic one. The official list for the ZWA 24-1 K shows T2A 1 904 521 341 and T1.25A 1 904 522 338; the one for the ZWA 24-1 A shows 2 A 1 904 521 341 and 1.25A 1 904 522 338. These are data for other variants: check those for your PCB.

Who should install it and what should I check before replacing it?

A qualified technician: it is the PCB of a gas boiler connected to the electrical network. Before replacing it, check the power supply, fuses, and connectors (general advice).

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Bosch PCB 8748300486 for Junkers ZWA 24 1KE23