BoilerFaultCodesVokera AL73 Fault Code
The Vokera AL73 fault code means: your boiler has detected a problem with the sensor that monitors the water temperature returning from your radiators, preventing the system from heating effectively.. It appears on 6 Vokera models in our database.
Technical description: Return thermistor fault
What causes the Vokera AL73 fault?
This fault occurs when the boiler's internal computer stops receiving a reliable signal from the sensor that monitors the temperature of the water returning to the unit. The most common reason is that the sensor itself has worn out and failed, or the electrical wiring connecting it to the main control board has developed a loose connection or a short circuit.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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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 31 August 2026