Main PCB Junkers Cerapur Compact ZWB 24-1/28-1 (Heatronic 3 Z 10003) Ref. 8 737 702 723
Main PCB Heatronic 3 (Z 10003) for Junkers Cerapur Compact ZWB/ZSB -1. It manages ignition, pump, fan, gas valve, and sensors. Useful when faults F0, A8, AC, b1, or EA appear and after ruling out sensors/wiring. Refurbished part with reference 8 737 702 723.
Junkers boilers compatible with reference 8 737 702 723
PCB with reference 8 737 702 723. Two confirmed compatibilities: ZWB 24-1 DE 23 and ZWB 28-1 DE 23.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Junkers ZWB 24-1 DE 23 | Cerapur Compact | Contrasted |
| Junkers ZWB 28-1 DE 23 | Cerapur Compact | 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 reference 8 737 702 723 is the part for your boiler.
The part reference, model, and equipment revision must be verified against the manufacturer's documentation.
Symptoms that require diagnosis on the PCB 8 737 702 723
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
F0 recurring or random
Cause: Internal fault of the Heatronic 3 PCB
Cut power, check connectors and bus; if F0 reappears with peripherals OK, replace the PCB.
- 02
b1 when turning on after maintenance
Cause: Incorrectly connected encoder or faulty reading on PCB.
Re-seat/measuring the encoder; if OK, the encoder input on the PCB may be damaged.
- 03
A8/AC with connected modules/controllers
Cause: Fault in Heatronic communication channel (PCB)
Test with another cable/bus; if the module works in another boiler, replace the PCB.
- 04
EA lock with spark and correct gas
Cause: Ignition/ionization stage on degraded PCB
Check electrodes and ground; if correct and without a recognized flame, check the PCB.
- 05
E9 despite being bled and with the pump operational
Cause: Erratic reading of NTC or thermal control on PCB
Measure NTC and continuity; check 24/5 V fuses on the PCB; if okay, replace the PCB.
Junkers fault codes that require diagnosis
| Code | Fault | Technical checks |
|---|---|---|
| F0 | Internal electronics fault | Check the plugs and bus module; if the issue persists, replace the PCB/module according to the manual. Directly related to the main board. |
| A8 | Communication interrupted (bus) | Check the wiring between the bus module and Heatronic; if the bus and peripherals are correct, there may be a fault in the PCB. |
| AC | Module not detected | Check the connection between the module and the Heatronic; if the module is OK, suspect the communication channel on the PCB. |
| b1 | Encoder connector not detected | Set/measure the encoder connector that identifies the model; if correct and still b1, likely fault in the PCB. |
| EA | Flame not detected (ignition lock) | Check gas, pressure, electrodes, and wiring; if spark/ionization are correct, check ignition stage/flame reading on the PCB. |
| E2 | Faulty outgoing NTC | Measure the NTC and its cable; if the values are correct, the analog input on the PCB may be damaged. |
| E9 | Overtemperature trip on supply | Bleed the system and check the pump; check the 24 V fuse on the PCB. If the hydraulics are correct, check the PCB. |
| F7/FA | Flame detected with burner off / false flame after closing gas | Dry/check electrodes and siphon; if false signal persists, check ionization circuit on 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 PCB 8 737 702 723
- Catalogue reference
- 8 737 702 723
- Uniclima internal SKU
- PECZWBC28X
- 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.
- Control platform
- Bosch Heatronic 3 (screen printing Z 10003)
- Reference on PCB
- 8 737 702 723 (8737702723)
- Equivalents/substitutes
- 8737707762; 8748300488 (supply/kit); 87377074270; 86389001340
- Fuses in electronics
- T 2.5 A AC 230 V; T 1.6 A DC 24 V; T 0.5 A DC 5 V (on PCB)
- Verified compatibility
- Cerapur Compact ZWB 24-1 DE 23; ZWB 28-1 DE 23 (ZSB/ZWB -1)
- Managed functions
- Ignition, flame detection, fan, pump, gas valve, NTC readings, and bus.
- Absolute cut-off of power and gas before intervening; verification of absence of voltage.
- Electrostatic discharge (ESD): handle the PCB with an anti-static wrist strap/mat.
- Bleeding the circuit after the replacement to avoid E9 due to air and overheating.
- Replace gaskets and single-use cable glands if associated elements are disassembled.
- Check and replace fuses with the same type/value; investigate the cause of the trip.
- Parameterization: check/adjust service functions of Heatronic 3 after replacement.
- Wiring and connectors: do not force; respect the guidelines and codifications of the original harness.
Frequently asked questions about the PCB 8 737 702 723
Is this PCB compatible with my Junkers Cerapur Compact boiler?
My boiler shows the fault code EA, could it be the PCB?
What reference should I look for if I need to replace my PCB?
How many models are compatible with this PCB?
Do I need to reprogram anything after changing the PCB?
I have seen other references like 87377074270, are they equivalent?
