Your boiler's internal communication system has lost power, meaning the different components cannot talk to each other to start the heating process.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: eBUS fault – voltage too low
What causes this fault?
This fault occurs when the internal communication line, which allows the display and controls to talk to the main brain of the boiler, loses electrical power. The most common reason is a short circuit in the wiring or a failing printed circuit board that is no longer able to distribute the correct voltage. It can also be triggered if an external smart thermostat or controller draws too much power from the system.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like FA9 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
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.
Affiliate links — we may earn a commission at no extra cost to you.