BoilerFaultCodesVokera A04 Fault Code
The Vokera A04 fault code means: your boiler has detected an internal electrical fault with the component that controls the gas supply, meaning it cannot safely ignite for heating or hot water.. It appears on 1 Vokera model in our database.
Technical description: Gas valve relay error
What causes the Vokera A04 fault?
This fault occurs when the boiler's main control board detects a communication failure or a physical defect in the relay that triggers the gas valve. Effectively, the brain of the boiler can no longer safely tell the gas valve to open or close, so it shuts down as a safety precaution. The most common reason is internal wear and tear on the printed circuit board's electrical components or a fault within the gas valve's solenoid.
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 A04 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera A04 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