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.

From this model's manual
Verified against the Worcester Bosch/Worcester Bosch Greenstar I Junior installation & service 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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All 38 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 light6a1213141516171819109115A8Blue indicator light flashingBlue indicator light offBlue light onDouble flash Blue lightEAERRORFAFast flashFast flash (Reset button Off)Fast flash / FlashingFast flash / Not a fault codeLOCKOUTNo lightNo light / Not a fault codeOff (No light)Off / OffOn / OffSlow flashSteady on (Burner lit)

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