Junkers Short cycling / premature shutdown

Boiler starts then shuts down after a few seconds without showing a code

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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

Oversized boiler, Poor circulation, Faulty temperature sensor, Incorrect minimum power setting, Blocked filter

How to Fix / Troubleshooting

Safety: Repeated cycling can stress components; address the cause promptly.

  • Check all radiators: Ensure enough radiators are open to absorb the boiler's minimum output.
  • Bleed and balance: Bleed radiators and balance the system to improve flow.
  • Clean filters: Clean any system or boiler-integrated filters/strainers.
  • Technician tasks:
    • Check NTC sensors for correct readings.
    • Adjust boiler minimum output and pump settings via the service menu.
    • Assess system design and consider adding a buffer or additional emitters if the boiler is significantly oversized.
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Repair Difficulty

Medium 3/5
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