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Worcester Bosch Greenstar 4000 Combi fault 2940

System fault burner control unit (low voltage)

Gas boiler

What it means

Low voltage condition detected at the burner control unit.

Likely causes

  1. Low supply voltage
  2. Faulty burner control unit
  3. Misfiring ignition transformer
  4. Incorrect gas type
  5. Incorrect gas supply pressure
  6. Power supply issue
  7. Faulty electrodes or cable
  8. Damaged or blocked flue system
  9. Incorrect gas/air ratio
  10. Faulty external gas flow monitor (natural gas)
  11. Faulty gas valve
  12. Faulty non-return valve in burner hood assembly
  13. Faulty seals around the burner
  14. Faulty internal flue seals
  15. Faulty case seals
  16. Flue system integrity problem
  17. Combustion circuit problem
  18. Combustion fault
  19. Cleaners containing chlorine or hydrogen halide (spray cans, primers, cleaners, paint, glue) stored or used near the appliance
  20. Build-up of dust

Where to start

  1. Restart appliance
  2. Check the ignition transformer function for misfiring in the Function check menu, Ignition test
  3. Check the gas type

The full answer, free

  • 55 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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