BoilerFaultCodesGlow-worm 19 Fault Code
The Glow-worm 19 fault code means: your boiler has stopped working because a sensor that monitors the temperature of the water in your heating system has become loose or disconnected from its pipe.. It appears on 4 Glow-worm models in our database.
Technical description: Central heating NTC not connected to pipe
What causes the Glow-worm 19 fault?
This fault occurs when the main temperature sensor responsible for monitoring the central heating water loses physical contact with the copper pipe it is designed to sit on. The most common reason is that the metal clip holding the sensor has weakened over time or been knocked loose, preventing the boiler from accurately measuring the water temperature. In some cases, the internal wiring has frayed or become disconnected, breaking the signal between the sensor and the main control board.
This fault often appears at the start of autumn when the heating system is first turned back on after summer, as the sudden vibration and thermal expansion in the pipes can cause a loose sensor to finally shift out of position.
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 19 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 19 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