BoilerFaultCodesVokera Yellow LED On, Red LED On Fault Code
Also written as YELLOWLEDONREDLEDON — same fault.
The Vokera Yellow LED On, Red LED On fault code means: your boiler has stopped working because the water pressure inside the system is too low to operate safely.. It appears on 1 Vokera model in our database.
Technical description: Zero pressure (Requires 're-pressurising')
What causes the Vokera Yellow LED On, Red LED On fault?
This fault occurs when the water pressure inside your heating system drops below a safe operating limit, causing the boiler to shut down to prevent internal overheating. Common reasons include a slow leak from a radiator valve or pipework, or a failure in the expansion vessel which allows the system pressure to escape through the safety discharge pipe.
This issue is frequently seen in autumn when the heating is turned back on for the first time, as the change in temperature can highlight small leaks or pressure losses developed over the summer.
DIY fix possible
Locate the filling loop, which is a silver braided flexible hose with one or sometimes two valves underneath the boiler.Open the valve(s) slowly to allow water into the system while watching the pressure gauge on the front panel.Close the valve(s) tightly once the needle reaches the green zone, typically between 1.0 and 1.5 bar.
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Gas Safe Register →Vokera models that show the Yellow LED On, Red LED On fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera Yellow LED On, Red LED On fault code information on this page is sourced and cross-checked against the official Vokera service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026