BoilerFaultCodesVokera 4070 Fault Code
The Vokera 4070 fault code means: your boiler has detected that the water temperature is too high and has shut down to prevent damage to its internal components.. It appears on 4 Vokera models in our database.
Technical description: Fault flow sensor over temperature – flow sensor flow/return line probe differential alarm
What causes the Vokera 4070 fault?
This fault occurs when the boiler's sensors detect that water is heating up far too quickly or staying too hot compared to the return flow. The most common reason is a circulation failure, often caused by a seized pump or a blockage in the heat exchanger that prevents water from moving through the system. It can also be triggered by a faulty sensor sending an incorrect temperature reading to the main control board.
This fault is more common in autumn when homeowners first turn their heating back on, as circulation pumps can often seize up after being idle during the summer months.
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 4070 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera 4070 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