F28
Glow-worm Ignition Failure (No Flame Detected)

Boiler shows F28, ignition fails, no flame established

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

No gas supply to boiler, Gas valve not opening, Air in gas line after interruption, Faulty ignition electrode or lead

How to Fix / Troubleshooting

Safety: Do not repeatedly reset the boiler if ignition fails. Isolate power and gas before internal work. Gas work must be done by a Gas Safe engineer.

  • Check gas supply: Confirm other gas appliances work. If not, contact your gas supplier. Ensure the boiler's gas isolation valve is fully open.
  • Reset once: Perform a single reset and listen for ignition clicks. If there is no clicking, the ignition system may be faulty.
  • Check meter and credit: For prepayment meters, ensure there is sufficient credit and that the meter is not locked out.
  • Engineer tasks:
    • Inspect and test the ignition electrode and cable.
    • Check gas valve operation and measure gas pressure.
    • Bleed air from gas line if recently worked on.

Do not attempt to dismantle gas components yourself; call a qualified engineer.

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Repair Difficulty

Professional Required 5/5

Required Part

Ignition Electrode
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