F29
Viessmann Flame dropout / unstable combustion

Flame lost during operation, boiler shuts down with flame failure 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

Fluctuating gas pressure, Blocked burner or injector, Fan speed instability, Partially blocked flue or air intake

How to Fix / Troubleshooting

Safety: Repeated flame loss can lead to unburned gas. Do not repeatedly reset without finding the cause.

  • Check gas supply stability: Note if other gas appliances flicker or go out. If so, contact your gas supplier.
  • Inspect flue terminal: Ensure the terminal is clear and not subject to strong wind recirculation.
  • Reset and observe: Reset the boiler and watch the flame through the inspection window (if present). If it is unstable or noisy, stop and call a technician.
  • Professional cleaning: A technician should clean the burner, check injectors, verify fan operation, and perform combustion analysis.
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Repair Difficulty

Professional Required 5/5

Required Part

MatriX Burner Assembly
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