Your boiler has detected an internal electrical fault with the component that controls the gas supply, meaning it cannot safely ignite.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Gas valve relay error
What causes this fault?
This fault occurs when the boiler's main control board detects a failure in the electrical circuit that opens and closes the gas valve. The most common reason is that the physical relay on the circuit board has worn out or become stuck, preventing the boiler from safely managing the flow of fuel. Because the system can no longer guarantee the gas will shut off correctly, it stops operating as a safety precaution.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like A05 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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