High
15 on Worcester Bosch Greenstar 24i / 28i Junior

Your boiler is struggling to switch between heating your radiators and providing hot water, which means you may lose one or both of these functions.

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

Diverter valve motor

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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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 light6a12131416171819109115A7A8b1Blue indicator light offEAERRORFAFast flashFast flash / FlashingFast flash / OffLOCKOUTNo lightNo light / Not a fault codeOff (No light)Off / OffOn / OffSlow flashSteady on (Burner lit)

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on a combi.

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Radiator not heating up

One cold radiator is usually a stuck valve pin or trapped air.

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Hot water works but heating does not

On a combi it is usually the diverter valve. On a system boiler, the motorised valve.

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