A13
Brötje
Bus communication fault (e.g., ISR/EMS/eBUS)
Boiler shows A13, no communication with room controller or EMS bus device
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Reversed polarity or short on bus wiring, Faulty room controller, Broken communication cable, Defective boiler control board bus interface
How to Fix / Troubleshooting
Safety: Disconnect power before altering control wiring.
- 1. Check controller power: Ensure the Brötje room controller or thermostat display is on. If blank, check its power supply or batteries.
- 2. Inspect bus wiring: At the boiler, verify that the bus wires are connected to the correct terminals and are not shorted. Follow the cable to the controller and check for damage.
- 3. Polarity: Some Brötje bus systems require correct polarity. Confirm wiring matches the installation manual.
- 4. Test with a known-good controller: If available, connect a spare Brötje controller directly at the boiler to rule out cable faults.
- 5. Control board: If wiring and controller are good, the boiler’s bus interface may be defective and require board replacement.
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Repair Difficulty
Medium
3/5
Required Part
Room Controller / Bus Interface
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