BoilerFaultCodesThere is a communication error between your boiler and its controls, often caused by an electrical wiring fault or a heavy load on the internal data connection.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: eBUS undervoltage: Short-circuit on eBUS input, eBUS overload or two power supplies with different polarities on the eBUS
What causes this fault?
This fault occurs when the electrical communication line between your boiler and its thermostat becomes overloaded or suffers a short circuit. It is often caused by damaged wiring, an incompatible external controller, or a component failure on the main circuit board that prevents the system from sending clear signals. Essentially, the boiler can no longer 'talk' to its controls, so it shuts down 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 F.49 — 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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