BoilerFaultCodesGlow-worm 14 Fault Code
The Glow-worm 14 fault code means: your boiler has likely overheated because the water isn't moving through the system properly or a sensor has detected an unsafe temperature.. It appears on 8 Glow-worm models in our database.
Technical description: TEMPERATURE LIMITER. CONTROLLED BY THE HEATING THERMISTOR ON FLOW PIPE: CHECK HEATING THERMISTOR (MAY BE UNCLIPPED) OR THREE WAY VALVE FAULTY. FAULTY PUMP. LOW HEATING FLOW RATE.
What causes the Glow-worm 14 fault?
This fault occurs when the boiler's internal sensors detect that the water temperature has exceeded a safe limit, causing the system to shut down for safety. The most common reason is a lack of water circulation, often caused by a failing pump or a stuck valve prevented water from leaving the boiler. It can also be caused by a simple sensor failure or a loose clip providing an inaccurate temperature reading.
This issue often surfaces when you first turn the heating back on in autumn, as internal moving parts like the pump or three-way valve can seize up after being idle throughout the summer.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Glow-worm models that show the 14 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 14 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026