BoilerFaultCodesVokera AL40 Fault Code
The Vokera AL40 fault code means: your boiler has stopped working because the water pressure in the central heating system has dropped too low.. It appears on 5 Vokera models in our database.
Technical description: Insufficient system water pressure
What causes the Vokera AL40 fault?
This fault occurs when the water pressure inside your heating system drops below the minimum level required for the boiler to operate safely. The most common reason is a slow leak from a radiator valve or pipework, but it can also happen if you have recently bled your radiators and haven't topped the system back up.
This issue is frequently seen at the start of autumn when homeowners turn their heating back on for the first time or bleed their radiators after months of inactivity.
DIY fix possible
Locate the external filling loop, which is usually a flexible silver hose with one or two small valves.Slowly open the valve(s) to allow water into the system while watching the pressure gauge.Close the valves tightly once the needle on the gauge reaches between 1.0 and 1.5 bar.
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Vokera models that show the AL40 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera AL40 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 31 August 2026