BoilerFaultCodesYour boiler has lost power to its main control board, which means the system cannot operate or provide heating and hot water.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Main supply to PCB 25B.
What causes this fault?
This fault occurs when the link between the boiler's external controls and its internal brain is broken, preventing electricity from reaching the main control board. The most common reason is a component failure on the board itself or a blown internal fuse, which acts as a safety measure if there has been an electrical surge. In some cases, loose or damaged wiring between the components can also stop the power flow.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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