BoilerFaultCodesGlow-worm Red neon on fascia illuminated Fault Code
Also written as REDNEONONFASCIAILLUMINATED — same fault.
The Glow-worm Red neon on fascia illuminated fault code means: your boiler has detected that the water pressure is too low to operate safely and has shut down to prevent damage.. It appears on 1 Glow-worm model in our database.
Technical description: Low water pressure. Fill central heating system, pressure 0.7bar min.
What causes the Glow-worm Red neon on fascia illuminated fault?
This fault occurs when the water inside your heating system drops below the minimum level required for the boiler to heat up safely. The most common reasons for this are a leak somewhere in your radiator pipework or the water expansion vessel losing its internal air pressure over time.
This issue often appears in autumn when the heating is turned on for the first time after summer, as stagnant joints may have developed small weeps or leaks.
DIY fix possible
Locate the filling loop, which is usually a silver flexible hose with two small valves.Slowly open both valves to allow fresh water into the system.Watch the pressure gauge and close both valves tightly once it reaches between 1.0 and 1.5 bar.
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Gas Safe Register →Glow-worm models that show the Red neon on fascia illuminated fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Red neon on fascia illuminated 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