BoilerFaultCodesVokera AL40 Fault Code
The Vokera AL40 fault code means: your boiler has detected that the water pressure in the central heating system is too low to operate safely and has shut down.. It appears on 4 Vokera models in our database.
Technical description: Insufficient system water pressure appliance operation
What causes the Vokera AL40 fault?
This fault occurs when the internal sensor detects that there isn't enough water pressure to safely circulate heat around your home. The most common reason is a slow leak somewhere in the radiator network or a drop in pressure following the bleeding of your radiators. In some cases, a component inside the boiler like the expansion vessel may have lost its charge, leaving the system unable to maintain steady levels.
This code is frequently seen at the start of autumn when homeowners turn their heating back on for the first time after summer, or after bleeding radiators for the winter months.
DIY fix possible
Locate the external filling loop, which is usually a flexible silver hose with one or two black taps underneath the boiler.Slowly open both taps (or one if there is only one) until you hear water flowing into the boiler.Watch the pressure gauge on the front of the boiler and close the taps once the needle reaches between 1.0 and 1.5 bar.Press the Reset button on the boiler control panel to clear the fault code.
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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 7 July 2026