F.28 / F28 — Vaillant ecoTEC exclusive 832/838

What it means: The boiler failed to light during its start-up attempts, so it has stopped.

Typical causes

  • Supply faults such as air in the gas, low pressure or a closed main cock
  • Faulty supply meter or pressure detector
  • Fault in the gas fitting or an incorrect gas setting
  • Ignition parts failing, such as the transformer, lead or plug
  • Flame sensing lost through the electrode, cable or poor earthing
  • Faulty electronics

When to treat it as unsafe

Treat as unsafe if a gas escape is suspected or the gas supply fault is not found; follow your Gas Safe procedure and the gas emergency notice on this page.

NwadFix is decision support. The engineer confirms every safety decision.

NwadFix is not affiliated with or endorsed by Vaillant. Manufacturer and model names are used only to identify the appliances an entry refers to.

Last reviewed: 13 October 2026 by a Gas Safe Engineer

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