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Worcester Bosch Greenstar 4000 Combi fault 2949

No flame signal with high output

Gas boiler

What it means

No flame signal at high output, potentially caused by strong winds or flue gas recirculation; burner restarts automatically after purging.

Likely causes

  1. Strong winds
  2. Flue gas recirculation
  3. Incorrect CO2 settings
  4. Faulty gaskets
  5. Low gas working pressure
  6. Incorrect gas type
  7. Incorrect gas supply pressure
  8. Damaged or blocked flue system
  9. Incorrect gas/air ratio
  10. Faulty gas valve
  11. Misfiring ignition transformer
  12. Power supply issue
  13. Faulty electrodes or cable
  14. Faulty external gas flow monitor (natural gas)
  15. Faulty burner
  16. Faulty seals around the burner
  17. Faulty internal flue seals
  18. Faulty case seals
  19. Flue system integrity problem
  20. Combustion circuit problem
  21. Combustion fault
  22. Damaged or insecure flue joints
  23. Obstructed or damaged terminal/terminal guard
  24. Damaged flue pipes or gaskets
  25. Unauthorised modification of flue gas system
  26. Leaking flue joints

Where to start

  1. Check the flue integrity
  2. Check the flue terminal position
  3. Check the CO2 settings and adjust if necessary

The full answer, free

  • 57 more checks in order
  • The readings and component tests from the manual
  • How to put it right, step by step
  • The manual page for this fault (page 77), right under the answer
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Safety: Isolate gas and power before you open the case. If you have been into the gas side, do a tightness test, and a combustion and flue check before you hand back. Gas Safe (UK) or RGI (Ireland) work only.

From the Worcester Bosch manual for the Greenstar 4000 Combi. Check the model on the data plate before you order parts.

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