High Lockout
P1 on Worcester Bosch Greenstar 25 HE Combi

Your boiler is struggling to start up because an internal electrical fuse has failed, cutting power to essential components.

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

Please wait, initialisation in progress. 24 V fuse blown. Replace fuse.

What causes this fault?

This fault occurs when an electrical surge or a short circuit within the boiler's internal components causes a safety fuse to blow. The most common reason is a failing component, such as a pump or valve, drawing too much power and overstraining the circuit to prevent further damage. It essentially acts as a protective shutdown to stop the delicate electronic control board from being fried.

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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Related fault codes

P2View →P3View →

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