Blue light: On / Lockout: Off High

Worcester Bosch Blue light: On / Lockout: Off Fault Code

Also written as BLUELIGHTONLOCKOUTOFF — same fault.

The Worcester Bosch Blue light: On / Lockout: Off fault code means: your boiler is receiving a request for heating but cannot start the sequence, even though your hot water is still working perfectly.. It appears on 2 Worcester Bosch models in our database.

Call an engineer soon

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

Technical description: Boiler not operating during central heating demand (HW ok)
Typical repair cost £120-250 (including labour)

Engineer required

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

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Worcester Bosch models that show the Blue light: On / Lockout: Off fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch Blue light: On / Lockout: Off fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026