High
F9 on Viessmann Vitodens 100-W BPJA 25kW P29

Your boiler's internal fan, which helps it burn gas safely, isn't starting up, so the boiler is shutting itself down to protect itself and will likely stop providing heating and hot water until it's checked by a qualified engineer.

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

Fan starts: No, after approx. 1 min – Check the fan, fan connecting cables, power at the fan and fan control

From this model's manual
Verified against the Viessmann/Viessmann Vitodens 100 W Bpja 5609913 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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Related fault codes

F4View →F5View →

All 21 fault codes on the Vitodens 100-W BPJA 25kW P29

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

5A3038515259b0b8E3E5F0F1F2F3F4F8FAFCFdFF

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