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Worcester Bosch Greenstar 4000 System fault 363

System fault boiler electronics / basic controller

Gas boiler

What it means

System fault relating to ionisation/electrode sensing circuit (V category fault).

Likely causes

  1. Faulty ionisation cable
  2. Faulty electrodes
  3. Faulty control unit/burner control unit
  4. Faulty ignition transformer
  5. Incorrect gas type
  6. Incorrect gas supply pressure
  7. Power supply fault
  8. Faulty electrodes/cable
  9. Faulty flue system
  10. Incorrect gas/air ratio
  11. Faulty external gas flow monitor (natural gas)
  12. Faulty burner
  13. Faulty air/gas ratio control valve

Where to start

  1. Check and replace the ionisation cable
  2. Check and replace the electrodes if required
  3. Check the ignition transformer function for misfiring in the Function check menu Ignition test

The full answer, free

  • 7 more checks in order
  • 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 System. Check the model on the data plate before you order parts.

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