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Glow-worm fault code

Glow-worm F1 Fault Code: What It Means and What to Do

On older Glow-worm boilers, such as the CI, CXi and HXi ranges, F1 is an ignition fault: the boiler could not light. Glow-worm says this usually relates to the gas supply, for example a prepayment meter out of credit, or a frozen or blocked condensate pipe. Newer Glow-worm boilers show the same problem as F28 or F29.

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What does F1 mean on a Glow-worm boiler?

Glow-worm’s published fault-finding tables for its CI, CXi and HXi ranges list F1 as “Ignition fault”. The boiler went through its start-up sequence but could not light the burner or prove the flame, so it locked out for safety.

Glow-worm’s homeowner guidance explains that on current boilers the equivalent codes are F28 and F29, and that this kind of fault usually relates to the gas supply, such as a pre-payment meter out of credit, or a condensate pipe that is frozen or blocked.

It matters which model you have, because Glow-worm codes changed over the years. Several websites wrongly describe Glow-worm F1 as low pressure; on these older ranges low pressure is F9, and on current boilers it is F22.

What causes an F1 ignition fault?

  • Gas supply: a prepayment meter out of credit, the gas turned off, or low gas pressure.
  • Condensate: a frozen or blocked condensate pipe or trap, very common on older condensing models in winter.
  • Ignition components: a worn spark electrode, a faulty ignition lead or the spark generator.
  • Flame detection: a dirty or failing flame sensing electrode.
  • Gas valve or fan: a gas valve that will not open properly, or a fan or air pressure fault that stops ignition. Fan faults usually show as F2 instead.

What can you safely check yourself?

  1. Check the gas. Does the hob light? Top up a prepayment meter if needed.
  2. Check the condensate pipe outside and thaw it with warm, never boiling, water if frozen. See frozen condensate pipe.
  3. Note your model name from the front of the boiler or the data badge.
  4. Reset once following your user manual.

When should you get an engineer?

If F1 returns after one reset with the gas on and the condensate pipe clear, the problem is with ignition inside the boiler. Older Glow-worm boilers are now well past their first decade, so the engineer will also look at the overall condition. They will test the gas pressure, electrodes, leads, gas valve and condensate trap, and you will get a price, and honest repair-or-replace advice, before any work starts.

What will the repair cost?

It depends on the part. Most boiler repairs cost £100 to £500 at typical UK market prices. The boiler repair cost guide breaks it down by fault, and the engineer gives you a price before any work starts. Send an enquiry to get one.

Glow-worm F1 fault code: common questions

Does F1 mean low pressure on a Glow-worm boiler?

Not according to Glow-worm's own fault tables for the CI, CXi and HXi ranges, which list F1 as an ignition fault. On those older models the water pressure code is F9; on current Glow-worm boilers it is F22. Check which model you have.

How do I reset a Glow-worm F1 fault?

Use the reset button as described in your user manual, once, after checking the gas supply and the condensate pipe. If F1 returns, leave the boiler off and send an enquiry with the model name.

My newer Glow-worm shows F28. Is that the same as F1?

Yes, broadly. Glow-worm explains that F28 and F29 on current boilers correspond to F1 on older appliances, and usually relate to the gas supply or a frozen or blocked condensate pipe.

Source: Glow-worm fault finding codes, CXi range ; Glow-worm, boiler fault codes and what to do if they occur . Fault code meanings can vary between models: check the manual for your boiler.

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