What does the Vaillant F.1 fault code mean?

Your boiler has failed to ignite, which means it cannot provide the heating or hot water you need.

How much does it cost to fix Vaillant error code F.1?

Typical repair cost for the Vaillant F.1 fault is £90-180 including labour.

Check if your gas supply is active (e.g., check other gas appliances or your meter credit)

Lack of gas, a fault with the ignition or flue – may need to adjust the gas valve or replace a defective electrode lead.

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

Almost always a stuck diverter valve on combis.

Lockout fault with a reset-needed pattern.

Older boilers — thermocouple, draught, gas supply.