BoilerFaultCodes.com
235 High Lockout

Your boiler's internal computer parts are having trouble communicating because they don't recognise each other's software versions.

Call an engineer soon

Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Conflicting versions of boiler electr. and boiler identification

What causes this fault?

This fault occurs when the boiler's main control board and its dedicated memory chip are running different, incompatible versions of software. It usually happens after a component has been replaced or if a power surge has corrupted the data that allows these parts to talk to each other. Without perfect synchronization between these two electronic brains, the boiler cannot safely verify its own model identity and will stop working.

Typical repair cost £120-£450 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Protect yourself from future repair bills

A boiler cover plan would cover faults like 235 — no call-out fees, no surprises.

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