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Worcester Bosch Greenstar 4000 Combi fault 306

Flame signal after closing the fuel supply

Gas boiler

What it means

Fault category V. Flame signal detected after closing the fuel supply.

Likely causes

  1. Faulty gas valve not sealing
  2. Faulty electrodes or connecting leads
  3. Faulty appliance electronics
  4. Incorrect gas type
  5. Incorrect gas supply pressure
  6. Damaged or blocked flue system
  7. Incorrect gas/air ratio
  8. Faulty gas valve
  9. Misfiring ignition transformer
  10. Power supply issue
  11. Faulty electrodes or cable
  12. Faulty external gas flow monitor (natural gas)
  13. Faulty burner
  14. Faulty seals around the burner
  15. Faulty internal flue seals
  16. Faulty case seals
  17. Combustion fault
  18. Restricted gas supply
  19. Livestock stables or storage rooms for fertilisers near appliance
  20. Permanent ammoniac concentration in installation area

Where to start

  1. Ensure the working pressure returns immediately to the standing pressure when the gas valve closes
  2. Check the gas valve
  3. Check electrodes and connecting leads

The full answer, free

  • 50 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 74), 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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