🕑 9 minutes read

Having a boiler fault is every homeowner's nightmare, especially during that cold winter when heating is essential. One common issue that Glow-worm boiler owners might encounter is the F1 fault code.

This is designed to help homeowners and landlords understand what the F1 fault code means, why it happens, and, most importantly, how to fix it. By the end of this guide, you'll have the expertise to resolve this issue and ensure your boiler runs smoothly again.

Understanding the F1 Glow-worm Boiler Fault Code

What Is F1 Glow-worm Boiler Fault?

When your Glow-worm boiler displays the F1 fault code, it signifies a problem with the system's ability to detect the presence of a flame. Essentially, the boiler is not recognising that it has ignited properly. This Glow-worm F1 fault is particularly relevant because it prevents the boiler from heating up your home or water, which can be highly inconvenient.

The F1 boiler fault Glow-worm is a safety feature designed to prevent potential damage to the boiler and ensure the safety of your home. Without this feature, an undetected flame failure could lead to more severe issues, including gas leaks or damage to the boiler components.

Causes of the Glow-worm Boiler F1 Fault

The F1 fault can be triggered by several factors, which makes diagnosing and fixing the issue a bit challenging. However, knowing the typical reasons can help you troubleshoot the issue more effectively.

Get professional assistance for your Glow-worm boiler repair in London.

Ignition Failure:

Ignition failure is a frequent issue in boilers and central heating systems, and it is often indicated by the F1 code.

Glow-worm F1 fault can be due to faulty components such as the ignition lead, electrode, or other ignition parts.

Specific parts like the spark electrode, probe, and ignition lead, which generate the spark to ignite the fuel, might be at fault. These parts are connected to the PCB (Printed Circuit Board) and other electrical components.

Boiler vibrations can loosen or damage these wires, leading to error codes, and sometimes vibrations are due to issues with larger components like the pump or fan.

Additionally, the lead, probe, and electrode may fail if your boiler is old, and even minimal water damage can cause malfunctions in these electrical components.

Gas Supply Issues:

Another culprit could be an issue with your gas supply.

If there's a disruption or lack of gas supply, the boiler won't ignite correctly.

However, if your gas regulator is frozen, an engineer can thaw it out. To prevent this issue in the future, insulating your meter box (often referred to as "lagging") is a good solution.

Blocked burner jets can also be easily fixed. They can be removed and cleaned without needing costly replacements.

On the other hand, if the gas valve gets stuck, it's usually more cost-effective to replace it rather than attempt to repair it. Once they start malfunctioning, stuck valves tend to cause repeated issues. The cost of a replacement gas valve will depend on your specific boiler model.


If you're considering a new boiler installation instead of repeatedly paying for issues with your Glow-worm boiler, call us for a professional and efficient service.

Flame Detection Problems:

The boiler uses a flame sensor to detect the presence of the flame. If this sensor is dirty or faulty, it may not correctly detect the flame.

Issues with the flame rectification process can also cause this problem.

Blocked Condensate Pipes

Modern boilers use ‘condensing technology’ to boost energy efficiency by repurposing heat lost during combustion. A critical component of this system is the condensate pipe, which drains the boiler's wastewater.

If this pipe gets blocked, it can prevent the boiler from functioning correctly and safely. This blockage is often caused by freezing temperatures, especially in the white plastic pipe located outside the house.

Safety Mechanism: The unit can detect blockages and stop excess water from being ignited, ensuring safe operation.

Check the condensate pipe regularly, particularly in cold weather, to ensure it's clear and positioned at a diagonal angle for proper drainage.

Faulty Fan

The fan plays a crucial role in removing harmful gases from the boiler and directing them into the flue pipe. For the heating process to begin, the PCB must first check the fan.

If there's a loose wire or an electrical fault in the fan, the PCB will shut down the system.

Modern fans come with multiple speed settings, making fan-related issues more common, especially in newer boiler models. By identifying the potential causes, you can approach the solution more systematically and solve the issue efficiently.

Call Serviceteam Heating Professionals

Contact Serviceteam Professionals for all your boiler needs. We offer round-the-clock service in London and handle emergency breakdowns and installations alike.

How to Fix a Glow-Worm Boiler F1 Fault?


Before attempting any fixes, ensure you're comfortable working with your boiler and understand basic safety precautions. If you're unsure, it's always best to seek professional help.

Here's a step-by-step guide to help you address the F1 boiler fault Glow-worm:

Check the Gas Supply

Start by ensuring that the gas supply to the boiler is on and that there are no interruptions. Check that other gas appliances in your home are functioning properly. If they aren't, the issue might be with your gas supply rather than the boiler itself.

If you suspect a gas leak, contact Serviceteam technicians immediately. We provide 24/7 emergency gas leak repair services in London and the surrounding areas.

Reset the Boiler:

Often, a simple reset can resolve the issue. Find the reset button on your boiler and press it gently. Wait for the boiler to go through its startup sequence and see if the F1 fault code disappears. If it reappears, you may need to investigate further.

Inspect the Flame Sensor and Ignition Components:

Turn off the boiler and allow it to cool down before inspecting the internal components. Check the flame sensor for dirt or damage. If it seems unclean, gently clean it with a soft cloth.

Inspect the ignition lead and electrode for any signs of wear or damage. If any components look faulty, they may need replacing.

Examine the Gas Valve and Pressure:

Ensure the gas valve is functioning correctly and that there's adequate gas pressure reaching the boiler. If you're unsure how to check this, we advise you to reach out to a certified technician to inspect the gas valve and pressure.

Unblock a Frozen Condensate Pipe

If your boiler condensate pipe is frozen, you might be able to defrost it yourself. Here's how:

  • Use Warm Water: Gently pour warm water over the frozen pipe. Do not use boiling water as it may harm the plastic pipe.
  • Hot Water Bottle: Alternatively, use a hot water bottle to warm the pipe slowly. After defrosting, turn on your boiler and clear any fault codes.
Seek Professional Help

If you've tried the above steps and the F1 fault persists, it's time to call in a professional.

A qualified gas-safe certified engineer can conduct a thorough inspection, diagnose the problem, and carry out any necessary repairs.

Dealing with a Glow-worm boiler F1 fault code can be frustrating, but understanding what it means and knowing how to fix it can make the process much smoother. By following the steps outlined in this guide, homeowners and landlords can address the issue effectively and ensure their boiler is back to working condition in no time.

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Call a Certified Gas-Safe Professional

Remember, while it's possible to fix some boiler issues yourself, don't hesitate to call in a professional if you're unsure or if the problem persists.

Our Serviceteam engineers are available round-the-clock, every day of the year, ready to assist you whenever you need help.

Contact us today for expert assistance and keep your home warm and comfortable!

For more details on boiler error codes, check out the boiler error code section on the Serviceteam blog.


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