E11
Klimosz Control Board / Internal Communication Fault

Boiler displays E11, no ignition, fan may not run.

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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

Defective main control PCB, Loose internal connectors, Voltage spikes or incorrect supply, Faulty low-voltage transformer on Klimosz board

How to Fix / Troubleshooting

Safety: Disconnect the boiler from mains power before touching any electronics.

  • Check supply voltage: Verify that the mains voltage at the boiler terminals is within the specified range (typically 230 V ±10%).
  • Inspect PCB connections: Remove the front panel and carefully check all plugs on the main control board. Reseat multi-pin connectors and look for burnt tracks or components.
  • Look for moisture: Signs of condensation or water on the PCB can cause faults. Dry the area and identify any leaks from the heat exchanger or pipes.
  • Reset boiler: After reseating connectors, restore power and perform a reset. If E11 returns immediately, the PCB is likely defective.
  • Replacement: PCB replacement should be done by an authorized Klimosz technician to ensure correct configuration and safety checks.
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Repair Difficulty

Professional Required 5/5

Required Part

Main Control PCB
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