Bosch PCB 8 748 301 340 for Junkers ZWA 24-1 K 31 Eurosmart

Application for the exact variant pending confirmation. Control board of the boiler. This unit has the circuit code 8 748 301 340, the integrated circuit J11743, and a board fuse T 1.25 A.

Type of part: PCBs (control boards)
Status: Refurbished
internal SKU: PLC226
Warranty: 1 year

VAT included Stock · 2 units

Compatibility

Junkers (Bosch) boilers compatible

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.

Junkers (Bosch) LeBlanc GVM 24-1/3 HNEI	Junkers (Bosch)	Unconfirmed
Junkers (Bosch) Junkers ZWA 24-1 K 31 Eurosmart	Junkers (Bosch)	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 printed on the soldering side of the PCB: 8 748 301 340 (8748301340).
Also check J11743 in the integrated circuit, the T 1.25 A fuse, and the HT II - 2a / DC AC CA label of the relay.
Just to confirm: Do not confuse it with 8 748 300 431 (official list of the ZWA 24-1 K) or with 8748300417, as they are different codes.
if they match, call us at 911 17 77 77 with the model of your boiler.

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.

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: Junkers (Bosch) PCB

Uniclima internal SKU: PLC226
Brand: Junkers (Bosch)
Type of part: PCBs (control boards)
Units in stock: 2 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.

PCB fuse: T1.25 A
Mounted relay label: HT II - 2a / CC CA CA
Marked integrated circuit: J11743
Handwritten marking on PCB: 489
Local adhesive label on PCB: 489
PCB marking on the solder side: 8 748 301 340
Manufacturer data for the boiler — PCB fuse: T 1.25 A · Manual ZWA 24-1 K 31
Manufacturer data for the boiler — Fuse reference: 1 904 522 338 · T 1.25 A · Official list ZWA 24-1 K
Manufacturer data for the boiler — Boiler supply: 230 V · 50 Hz · Manual ZWA 24-1 K 31
Identification — Marked integrated circuit: J11743
Identification — Local handwritten marking on PCB: 489
Identification — Local adhesive label on PCB: 489
Identification — PCB marking on solder side: 8 748 301 340
Technical sheet: PCB fuse: T1.25 A
Technical sheet: Relay mounted label: HT II - 2a / CC CA CA
Pending applications to verify: Junkers ZWA 24-1 K 31 Eurosmart — compatibility noted; pending confirmation by variant.

Before purchasing

To confirm: LeBlanc GVM 24-1/3 HNEI — Italian from the PCB 87483005610 for GVM HNBI/HNEI; a forum thread (1 source) mentions 8748301340 with this boiler; without
Not compatible or excluded by default: Junkers ZWA 24-1 A — It has a different PCB: 8 748 300 496 (official list)
Not compatible or excluded at source: Junkers ZWA 24-1 KM — It has a different PCB: 8 748 300 561 0 (third-party breakdown)
Do not confuse: 8 748 300 431 — PCB of the ZWA 24-1 K family in the official list — It is a different code: it does not appear in this unit, which has 8 748 301 340. Do not assume they are the same without comparing.
Do not confuse: 8748300417 — PCB provided for the ZWA 24-1 K (formerly 8748300496 in one); a 3rd one is written 88748300417 — It is another code: it does not appear in this unit. Compare before ordering.
The official list for the ZWA 24-1 K gives 8 748 300 431 for the PCB, in the text read, 8 748 301 340 does not appear; 8748300417 and a third one is written as 88748300417. Compare the code printed on your PCB.
To be confirmed: The boiler confirms it; the code and the PCB support it. The official list and other PCB codes for the ZWA 24-1 K.
Pending registered applications to confirm by model, variant, or programming: Junkers ZWA 24-1 K 31 Eurosmart.

Frequently Asked Questions

Frequently asked questions about the PCB (control board)

Where is the code for this PCB and what else should I compare?

The 8 748 301 340 is printed on the solder side of the circuit (they write it as 8748301340). Also, compare J11743 on the integrated circuit, the fuse T 1.25 A, and the label HT II - 2a / DC AC AC of the relay.

Is it compatible with my Junkers ZWA 24-1 K 31 Eurosmart?

The compatibility of this variant is pending confirmation. Registered: for that boiler. The official spare parts list (ed. 02.08) includes the ZWA 24-1 K 31 (ZWA24-1K31S2892 for Spain), but it lists another PCB, the 8 748 300 431, and the 8 748 301 340 does not appear in the text read. For the ZWA 24-1 K, there is another PCB, the 8748300417; a third one is written as 88748300417. Compare the code printed on your PCB.

What is the difference between 8 748 301 340 and other Eurosmart PCB codes?

The compatibility of this variant is pending confirmation. To be confirmed: The 8 748 300 431 is the PCB ("Printed circuit", pos. 4) from the official list of the ZWA 24-1 K. The official list of the ZWA 24-1 A provides the 8 748 300 496, and a third-party breakdown gives the 8 748 300 561 0 for the KM. The 8 748 301 340 does not appear in the text read from those three lists, although it is registered: for the K 31. We cannot say that it replaces another. It also cites the 8748300485 alongside the 8748301340 (1 source).

What do J11743, 489, 8748300489, and HT II - 2a / CC CA CA mean?

To confirm: J11743 is the marking of the integrated circuit, 489 is a handwritten marking and an adhesive label on the PCB, and HT II - 2a / CC CA CA is the label of the mounted relay. 8748300489 is the inventory reference; that code corresponds to the refurbished PCB of a Worcester 24Si II / 28Si II. They do not necessarily correspond to a spare part reference.

What fuse does it use and what should I check when installing it?

It uses a T 1.25 A fuse. The manual for the ZWA 24-1 K 31 and the official list (1 904 522 338) provide the same value. The manual places the maintenance potentiometer (pump mode or maximum heating power) behind the coding connector.

Is it compatible with other boilers?

The compatibility of this variant is pending confirmation. To be confirmed: It is only registered for the ZWA 24-1 K 31. The official list for the ZWA 24-1 A provides a different PCB (8 748 300 496), and a third-party breakdown gives another one for the KM (8 748 300 561 0). A forum thread cites 8748301340 for a LeBlanc GVM24-1/3 HNEI, but the Italian source provides 87483005610. For another boiler, please send us a photo of your PCB and the boiler from Contact.

Who should install it?

A qualified technician. The boiler is powered at 230 V · 50 Hz, according to the manual, and operates with gas. Before replacing the PCB, it is advisable to check the fuse T 1.25 A.

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Bosch PCB 8 748 301 340 for Junkers ZWA 24-1 K 31 Eurosmart