BoilerFaultCodesYour boiler has shut down because it lost power while it was already trying to deal with an internal safety error.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: The mains voltage was interrupted during an interlocking fault
What causes this fault?
This fault occurs when your boiler loses its electrical connection at the exact moment it was trying to handle a separate internal safety issue. It effectively means the boiler's computer has become confused and entered a protective shutdown because it couldn't finish its safety check. The root cause is usually a loose connection in the wiring or a failing electronic control board that can no longer process power signals correctly.
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.
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A boiler cover plan would cover faults like FD231 — no call-out fees, no surprises.
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Worcester Bosch GB162 is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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