What does the Viessmann F5 fault code mean?

Your boiler is struggling to confirm that air is flowing correctly through its internal system, which prevents it from safely starting the burner.

How much does it cost to fix Viessmann error code F5?

Typical repair cost for the Viessmann F5 fault is £150-350 including labour.

Air pressure switch does not open at burner start or does not close when ignition speed is reached

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Six most common causes of dropping pressure.

Each noise points to a different fault.

Safety-critical — turn off, read this.