High
8 flashes on Worcester Bosch Greenstar 25CDi

Your boiler is failing to light because it cannot detect a flame, meaning your heating and hot water will not work.

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

Flame not detected. Is gas cock turned on? Check gas supply pressure, power supply, igniter electrode and lead, ionisation sensing electrode and lead, flue duct and COo level.

From this model's manual
Verified against the Worcester Bosch/Worcester Bosch Greenstar 25cdi 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 21 fault codes on the Greenstar 25CDi

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

2 flashes3 flashes4 flashes5 flashes6 flashes7 flashes9 flashesA7b1C6CH flow NTC sensor defective.Code plug not detected.E2E9F7Fan speed too low.Flame not detected.Internal error.Rapid flashesSlow flashes

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