High Lockout
FAIL POINT B on Worcester Bosch 24/28CDi II RSF

Your boiler has lost power or has a serious internal electronic failure, meaning it cannot start the ignition process to provide heating or hot water.

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

No green light (Red lights function)

What causes this fault?

This fault occurs when the boiler's control system loses its vital electrical feed, preventing it from managing the heating process. The most common reason is a blown internal fuse or a failure within the Printed Circuit Board (PCB) which acts as the boiler's brain. In some cases, a faulty transformer is unable to convert power correctly, leading to a total loss of the green operation light.

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

FAIL POINT AView →FAIL POINT CView →

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