BoilerFaultCodesGlow-worm F18 Fault Code
The Glow-worm F18 fault code means: your boiler's control panel has stopped communicating with the main computer, meaning you cannot adjust settings or see what the boiler is doing.. It appears on 1 Glow-worm model in our database.
Technical description: User interface fault
What causes the Glow-worm F18 fault?
This fault occurs when the data link between the display screen and the boiler's internal computer is broken or interrupted. The most common cause is a loose connection or damaged wiring inside the unit, though a hardware failure on one of the circuit boards can also prevent the components from talking to each other.
DIY fix possible
Switch the boiler off at the main electrical fused spur switchWait for 30 secondsSwitch the power back on to see if the control screen resets and clears the error
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Gas Safe Register →Glow-worm models that show the F18 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F18 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