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Worcester Bosch Greenstar 4000 Combi fault 2923

Boiler electr. system fault (unexpected feedback from modulating gas valve)

Gas boiler

What it means

Unexpected feedback signal detected from the modulating/current controlled gas valve.

Likely causes

  1. Faulty gas valve
  2. Damaged harness
  3. Faulty appliance electronics (control unit)
  4. Incorrect gas type
  5. Incorrect gas supply pressure
  6. Damaged or blocked flue system
  7. Incorrect gas/air ratio
  8. Misfiring ignition transformer
  9. Power supply issue
  10. Faulty electrodes or cable
  11. Faulty external gas flow monitor (natural gas)
  12. Faulty burner
  13. Faulty seals around the burner
  14. Faulty internal flue seals
  15. Faulty case seals
  16. Combustion fault
  17. Restricted gas supply
  18. Livestock stables or storage rooms for fertilisers near appliance
  19. Permanent ammoniac concentration in installation area

Where to start

  1. Check the voltage to the gas valve
  2. Check the continuity of harness
  3. Check the resistance of the gas valve coils

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 76), 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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