BoilerFaultCodesIdeal Low system pressure neon lit Fault Code
Also written as LOWSYSTEMPRESSURENEONLIT — same fault.
The Ideal Low system pressure neon lit fault code means: your boiler has detected that there is not enough water in the central heating system to operate safely, so it has shut down to protect itself.. It appears on 1 Ideal model in our database.
Technical description: The low system pressure neon is illuminated, indicating the system pressure is too low.
What causes the Ideal Low system pressure neon lit fault?
This fault occurs when the water levels inside your radiators and pipework drop below a functional level, meaning the boiler can no longer circulate heat safely. The most common reason is a tiny leak somewhere in the system or because the air was recently bled out of your radiators without topping the water back up. In some cases, a failing internal component like the expansion vessel may be causing the pressure to fluctuate and escape.
This issue often surfaces when you turn your heating back on for the first time in autumn, as the system settles after being dormant all summer.
DIY fix possible
Locate the filling loop, which is usually a flexible silver hose with two small valves underneath the boiler.Slowly open both valve handles until you hear water entering the system.Watch the pressure gauge and close both valves tightly once the needle reaches 1.5 bar.
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Gas Safe Register →Ideal models that show the Low system pressure neon lit fault code
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Source
Ideal Low system pressure neon lit fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026