High
Fast flash / Off on Worcester Bosch Greenstar 24i / 28i Junior

Your boiler has detected a critical internal error and purposefully shut itself down to prevent damage, meaning you currently have no 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.

What the manual says

Manufacturer manual

Volatile lockout - Temperature sensor (8000-20,000Ω). Low voltage wiring harness / connections to sensor. Fan / fan harness / connections to fan. Code plug fitted.

Shared across the Greenstar range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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Boiler cover options

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A cover plan would handle faults like Fast flash / Off: no call-out fees, no surprise bills.

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All 35 fault codes on the Greenstar 24i / 28i Junior

Seeing a different code? Every code this model can display, in one place.

2 pulses2 pulses / No light2 pulses No light5 pulses5 pulses / No light5 pulses No light6a1213141516171819109115A7A8b1Blue indicator light offEAERRORFAFast flashFast flash / FlashingLOCKOUTNo lightNo light / Not a fault codeOff (No light)Off / OffOn / OffSlow flashSteady on (Burner lit)

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