BoilerFaultCodesYour boiler's internal computer has encountered a software logic error and has stopped working to prevent any further issues.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Alternating Software Sequence Error
What causes this fault?
This fault occurs when the boiler's main control board loses its place in its operating sequence or receives conflicting data from its sensors. The most common reason is an internal electronic failure within the circuit board or a loose connection in the wiring harness that prevents the computer from safely moving to the next stage of the ignition process.
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 LED 1 & 2 Alternating Slow Flashing (2Hz) — no call-out fees, no surprises.
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