High Lockout
FAIL POINT E on Worcester Bosch Greenstar Si

Your boiler has detected a problem with the internal sensor that tells it when to provide hot water, meaning you currently have no hot water when you turn your taps on.

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

Hot water mode failure. Flowswitch assembly lever not activating microswitch, or microswitch/wiring/continuity failure across contacts 19 and 20.

What causes this fault?

This fault occurs when a small internal part called a flowswitch fails to move or signal the boiler when you turn on a hot tap. Over time, the internal mechanical components can become stuck or the electrical switch attached to it can wear out, preventing the boiler from knowing it needs to fire up for hot water. In some cases, it may also be caused by a loose connection or a fault in the wiring that carries this signal to the main control board.

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 BView →FAIL POINT DView →

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