BoilerFaultCodesGlow-worm 0.3 bar (flashing) Fault Code
Also written as 03BARFLASHING — same fault.
The Glow-worm 0.3 bar (flashing) fault code means: your boiler has lost the water pressure it needs to work, so it has safely shut itself down until you top it back up.. It appears on 1 Glow-worm model in our database.
Technical description: Insufficient system pressure. The system pressure is low and must be re-filled.
DIY fix possible
Locate the filling loop, which is a silver braided hose connecting two pipes underneath the boiler.Open the valves on both ends of the hose to let water into the system.Keep an eye on the pressure gauge and close both valves firmly once it reaches 1.5 bar.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like 0.3 bar (flashing): no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Glow-worm models that show the 0.3 bar (flashing) fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm 0.3 bar (flashing) 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 7 July 2026