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Glow Worm Boiler Fault Codes F1 – F3 – F4 – F9 – F14 – F16 Explained

Understanding Glow-worm Boiler Fault Codes

Glow-worm boilers are known for their reliability, but like any appliance, they can encounter issues from time to time. Understanding what different fault codes mean can save you time, money, and hassle in resolving problems promptly. Let’s delve into some common Glow-worm boiler fault codes and their meanings.

F1 Error Code: Ignition Sequence Problem

Encountering the F1 fault code on your Glow-worm boiler indicates an issue with the ignition sequence. This fault code signals that your boiler’s ignition process has encountered a problem. Various ignition issues could lead to your boiler ceasing to work efficiently. It’s crucial to address this promptly to ensure your boiler operates smoothly.

F3 Fault Code: Fan Speed Issue

If your Glow-worm boiler displays the F3 fault code, it suggests that the fan is unable to attain the required ignition speed. This can occur due to mechanical malfunctions or loose wiring within the boiler system. Prompt inspection and resolution are necessary to restore proper functionality to your boiler.

F4 Fault Code: Minor Blockage Issue

The F4 fault code on Glow-worm boilers typically indicates a minor blockage that can be swiftly resolved. Unlike issues related to the gas boiler, this fault can often be fixed without the need for a Gas Safe registered professional. It’s a relief to homeowners as it doesn’t pose significant safety concerns.

F9 Fault Code: Generic Yet Troublesome

Among homeowners and engineers, the F9 fault code is dreaded due to its generic nature, encompassing various faults from diverter valve issues to circulation and pressure problems. Often, inadequate system flushing leads to sludge buildup in the plate heat exchanger, necessitating flushing, pressure adjustments, or even pump replacements by a professional engineer.

F14 Fault Code: Misleading Gas Valve Issue

Encountering an F14 fault code on your Flexicom CX boiler might initially point to a defective gas valve according to the manual. However, this isn’t always the case. Consulting with an engineer can determine whether a new gas valve, wiring harness, or PCB is required for resolution.

F16 Fault Code: Flame Detection Concerns

If your Glowworm Ci model displays the F16 fault code, it indicates a flame detection fault. Proper servicing and potential replacement or cleaning of the probe may be necessary to ensure proper boiler function. Ignition issues may also contribute to this fault, which can be rectified by a qualified engineer.


Understanding Glow-worm boiler fault codes empowers homeowners to address issues promptly and effectively. While some faults may seem daunting, consulting with qualified professionals ensures efficient resolution, restoring your boiler’s performance and maintaining household comfort.

By providing detailed insights into common Glow-worm boiler fault codes, we aim to assist homeowners in troubleshooting issues effectively and efficiently. Stay tuned for more informative articles on boiler maintenance and troubleshooting tips! Response Boilers Liverpool are a professional local family-operated boiler repair servicing and new boiler installer in Liverpool

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