View Junkers faults by model and generation
On the Eurosmart ZWA 24-1 AM 23/31, the reset button indicates groups of faults by its flashing frequency. Note the flashes per second and whether hot water, heating or both are unavailable; do not count individual flashes separated by a pause.
Junkers Eurosmart symptoms and faults
Flashes once per second: 1 HzThe 1 Hz group covers ignition, overheating and internal faults.
Possible causes include gas supply and pressure, spark, pump, water pressure, limit thermostat, burner, heat exchanger, wiring or control board; the same rate groups different checks.
Source: Junkers Eurosmart 6 720 611 372 E (04.04), section 9.1, table 7 · page 32.
Flashes four times per second: 4 HzThe 4 Hz group includes signals from sensors and the flue circuit, among other things.
The manufacturer lists the coding plug, heating or DHW NTC, pressure switch and condensation in its tubes, fan, flue/air intake, wiring and electronics among the items to check.
Source: Junkers Eurosmart 6 720 611 372 E (04.04), section 9.1, table 7 · page 33.
Flashes eight times per second: 8 HzThe 8 Hz signal is associated with the operating-mode switch being set to Min. or Max.
This is an internal adjustment condition that must be checked by a professional; it is not an instruction to replace a part.
Source: Junkers Eurosmart 6 720 611 372 E (04.04), section 9.1, table 7; control-panel figure · pages 21, 33.
No hot water, but heating worksThe manual distinguishes this symptom from loss of both services.
For a DHW fault, it lists the flow sensor or turbine, hot-water NTC and control board; a 4 Hz flash may occur when the NTC is the cause.
Source: Junkers Eurosmart 6 720 611 372 E (04.04), section 9.1, table 7 · page 32.
Radiators stay cold, but hot water worksA heating-only fault points towards the heat demand and its control.
The table lists the LS/LR connection or its signal, the room thermostat and the control board; describe whether the problem starts when heating is requested.
Source: Junkers Eurosmart 6 720 611 372 E (04.04), section 9.1, table 7 · page 32.
No indicator lights come on when heat is requestedNo indicator lights are distinguished from a lockout with flashing.
The manufacturer lists the power supply, fuse, transformer, connections and printed circuit board; checking them is part of the boiler's electrical diagnosis.
Source: Junkers Eurosmart 6 720 611 372 E (04.04), section 9.1, table 7 · page 32.
What to observe: identify the full model, record the panel indication and distinguish whether hot water, heating or both are failing. The indication guides the checks; the diagnosis determines the repair.
Eurosmart fault-indicator flashes
| Frequency | Manual guidance | Next step |
|---|---|---|
| 1 Hz: once per second | Covers ignition, overheating and internal faults, with several possible causes. | Describe when the lockout occurs and which service stops working; diagnosis is required. |
| 4 Hz: four times per second | Includes the coding plug, sensors, pressure switch, fan, flue system, wiring and electronics. | Report the observed rate. It does not by itself identify which component should be replaced. |
| 8 Hz: eight times per second | Points to the operating-mode selector being in the Min. or Max. position. | Request a professional inspection; do not open the appliance or change internal settings. |
These are frequencies per second, not groups of one, four or eight flashes separated by a pause. If you cannot distinguish the rate, send a short video of the panel instead of assigning it a number.
No hot water, no heating, or neither service
Describe which function is failing: hot water while heating still works, heating while hot water remains available, or neither service. Add whether the indicator lights come on and whether the fault appears when a hot-water tap is opened or heat is requested. The manual lists these symptoms separately in its fault table.
To prepare for the enquiry, say when the problem began, whether it is continuous or intermittent, and what was last done to the appliance. A photo of the rating plate and another of the panel help distinguish this appliance from another Eurosmart. Record the accessible pressure-gauge reading without touching components.
Eurosmart repairs and choosing spare parts
The indicator helps describe the problem. Choosing a spare part requires a diagnosis and the references for the appliance and component. Two parts being listed under the Junkers brand does not prove that they are interchangeable.
- Enquire about repairing a Junkers boiler
- Junkers circuit-board catalogue
- Junkers pump catalogue
- Junkers flue fan catalogue
Questions about Junkers Eurosmart faults
They are flashing frequencies of the reset button described in the manual's fault table: 1 Hz groups several ignition, temperature, component and control faults; 4 Hz groups other sensor, pressure-switch, ventilation, flue or control conditions; and 8 Hz is associated with the switch set to Min. or Max. They are not alphanumeric fault codes.
No. The manual lists several possibilities for 4 Hz, including the NTC, differential pressure switch, tubes, fan, flue, wiring and control board. Checks are needed to determine which applies.
For the ZWA 24-1 AM, the manual's table lists the flow sensor, hot-water NTC or control board among the possible causes. The table does not identify the fault without the corresponding checks.
No. The flashing signal classifies a group of faults; even when the manual lists parts, the specific variant must be diagnosed before choosing a spare part.
If you smell gas, avoid flames and electrical switches, and call your gas supplier's emergency service from a safe place.
Manual and scope of this guide
Source: Eurosmart installation and operating manual, edition 6 720 611 372 E (04.04). Model types: page 4; panel: figure 27 on page 21; fault finding: section 9.1 and table 7 on pages 32–33. If the full model or panel differs, check the documentation for that specific appliance.
- Official Bosch/Junkers manual for Eurosmart ZWA 24-1 AM 23 and AM 31
Eurosmart ZWA 24-1 AM 23/31
Document editing
For the variants ZWA 24-1 AM 23 and AM 31. Fault table: pages 32–33.
More Junkers boiler guides
Choose by full model number. Each guide has its own scope and is not an interchangeable code chart for the Eurosmart.