Glow-worm F1 Fault Code: What It Means And How To Fix It

If your Glow-worm boiler is showing an F1 fault code or F1 error code, it usually means the boiler has failed to detect a flame. The boiler locks out and stops working until it has been reset and the cause dealt with.

We’re Hinckley Plumbing & Heating — Gas Safe registered engineers covering Hinckley, Nuneaton, Leicester, Tamworth, Coventry, Rugby, and Loughborough — and this guide explains what the Glow-worm F1 fault code on a boiler means, the most common causes, what you can safely check, and when to call us.

What Does The Glow-worm F1 Fault Code Mean?

The Glow-worm F1 fault code is a no flame detected fault. The boiler has run its ignition sequence, but the flame sensor has not confirmed that a flame is present.

It’s worth being clear on one thing: F1 means different things on different brands. On an Ideal boiler, F1 is a low pressure fault. On Glow-worm — including the Energy, Ultimate and Betacom ranges — F1 is about ignition. Same code, different problem.

What Is The Glow-worm F1 Error Code On A Boiler?

The Glow-worm F1 error code on a boiler is another way of saying the boiler tried to light and couldn’t confirm that it had.

In plain English: gas was called for, the boiler sparked, and the sensor saw nothing. Instead of trying again indefinitely, the boiler stops and shows F1.

What Causes The Glow-worm F1 Fault Code?

The most common causes of the Glow-worm F1 fault code on a boiler are:

• No gas reaching the boiler
• A gas meter or emergency control valve turned off
• A prepayment meter with no credit
• A frozen condensate pipe
• Worn, dirty, or misaligned ignition electrodes
• Damaged ignition leads
• A faulty gas valve
• A blocked or restricted flue
• A faulty PCB

The first four are worth a look yourself. The rest need a Gas Safe registered engineer.

Is The Glow-worm F1 Fault Dangerous?

The lockout itself is a safety feature doing exactly what it should — stopping the boiler rather than letting it keep releasing gas it can’t burn.

If you can smell gas at any point, don’t touch the boiler. Turn the gas off at the meter if it’s safe to do so, open windows, avoid light switches, and call the National Gas Emergency Service on 0800 111 999.

How To Fix The Glow-worm F1 Fault Code

A handful of safe checks first.

1. Check whether your other gas appliances are working. If the hob and gas fire are dead too, the issue is the gas supply, not the boiler.
2. Check the gas meter is switched on and, if you’re on a prepayment meter, that there’s credit.
3. In cold weather, check the condensate pipe — the white plastic pipe running from the boiler to an outside drain.
4. If it’s frozen, thaw it with warm water poured along its length, or a hot water bottle held against it. Never use boiling water, as it can crack the pipe.
5. Press and hold the reset button, then give the boiler a minute to attempt ignition.

If it fires and stays running, you’re done. If it locks out again, leave it there.

Don’t reset repeatedly — two or three attempts at most. A boiler that keeps failing to light isn’t going to be fixed by another button press.

Why Does The Glow-worm F1 Error Code Keep Coming Back?

If the F1 error code clears on a reset but returns, something is stopping reliable ignition each time.

Ignition electrodes are the usual suspect. They wear down, carbon up, or shift out of the correct gap over years of firing, and they’re a routine replacement part. Gas valves fail less often but cause the same code. A partially blocked flue or a condensate pipe that only freezes in the coldest hours can make the fault feel intermittent and unpredictable.

When Should You Call Us About A Glow-worm F1 Boiler Fault?

Call Hinckley Plumbing & Heating if:

• Other gas appliances work fine but the boiler still shows F1
• The F1 fault code returns after a reset
• The condensate pipe is clear but the fault persists
• You can hear clicking from the boiler with no ignition
• The boiler lights briefly then cuts out
• The fault comes and goes over days or weeks

Anything inside the boiler casing is Gas Safe work. It’s illegal for anyone not on the Gas Safe Register to carry it out, including taking the front cover off.

Book A Glow-worm Boiler Fault Check

If your Glow-worm boiler is showing an F1 fault code or F1 error code, we can help.

We cover Hinckley, Nuneaton, Leicester, Tamworth, Coventry, Rugby, and Loughborough, and we’ll give you a clear, honest assessment of whether it’s a gas supply problem, a worn electrode, or something more involved. Call us or use our contact form to book a boiler inspection.

Glow-worm F1 Fault Code FAQs

Is Glow-worm F1 the same as Ideal F1?

No. On Glow-worm boilers F1 is an ignition or flame detection fault. On Ideal boilers F1 means low water pressure. Always check against your own manual.

Can I fix the Glow-worm F1 fault code myself?

Only the basic checks — gas supply, meter credit, and a frozen condensate pipe. Anything else needs an engineer.

Why does my Glow-worm boiler show F1 only in winter?

That usually points to a frozen condensate pipe, which is one of the most common causes of ignition lockout in cold weather.

Will the Glow-worm F1 error code go away on its own?

Usually no. It needs a reset, and it will keep returning until the underlying cause is fixed.