High Lockout
Mains On neon NOT lit on Ideal Response

Your boiler has no power and is completely unresponsive, likely due to an electrical supply issue or a blown fuse.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Check connections and continuity of EMC filter or rectify external fault.

What causes this fault?

This fault occurs when electrical power fails to reach the boiler's internal controls, leaving the unit completely lifeless. The most common reason is a blown fuse in the external wall switch or a surge that has tripped the boiler's internal protection, often caused by a failing component like the pump or fan. In some cases, the interference filter has failed, preventing electricity from flowing through the circuit safely.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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