BoilerFaultCodesVokera AL73 Fault Code
The Vokera AL73 fault code means: your boiler has stopped working because it cannot correctly measure the temperature of the water coming back from your radiators.. It appears on 8 Vokera models in our database.
Technical description: Return sensor fault
What causes the Vokera AL73 fault?
This fault occurs when the boiler's control board loses communication with the sensor that monitors water returning from your heating system. The most common reason is that the internal sensor has developed a chemical failure or electrical short, preventing the boiler from knowing if it is safe to continue firing. In some cases, it can also be caused by loose or damaged wiring connecting that sensor to the main computer.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Vokera models that show the AL73 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera AL73 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