BoilerFaultCodesGlow-worm Red neon on fascia Fault Code
Also written as REDNEONONFASCIA — same fault.
The Glow-worm Red neon on fascia fault code means: your boiler has stopped working because the water pressure in the central heating system is too low.. 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 fault?
This fault occurs when the water level inside your central heating system drops too low for the boiler to operate safely. It is usually caused by a small leak in the pipework or radiators, or because the air cushion inside the expansion vessel has depleted over time.
This issue often surfaces in autumn when the heating is turned on for the first time after summer, as the change in temperature can highlight existing pressure drops.
DIY fix possible
Locate the filling loop, which is usually a silver flexible hose with one or two small taps.Slowly open the tap(s) until you hear water entering the system.Watch the pressure gauge and close the taps firmly once it reaches between 1.0 and 1.5 bar.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Glow-worm models that show the Red neon on fascia fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm Red neon on fascia 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