High
F5 on Viessmann Vitopend 100

Your boiler is struggling to clear exhaust gases or draw in fresh air because a sensor is detecting an airflow issue during startup.

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

Burner control unit fault The air pressure switch is closed during the burner start or does not close when the ignition load has been reached

From this model's manual
Verified against the Viessmann Vitopend 100 installation & service manual, page 37.
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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