What does the Vaillant Home F91 fault code mean?
The F91 fault code indicates a system ignition fault in the Vaillant Home boiler. This typically means that the boiler is unable to ignite the burner, preventing it from heating water or providing central heating.
Common Causes
- Blocked Flue: A blockage in the flue can prevent proper ventilation, leading to ignition failure.
- Faulty Ignition Electrode: If the ignition electrode is damaged or malfunctioning, it may not produce the necessary spark to ignite the gas.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for any gas or electrical issues, as these can be dangerous. However, if you suspect low pressure, you can check the pressure gauge and reset the boiler if necessary.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving an F91 fault could be around £150 to £250, depending on whether the ignition electrode needs replacing or if a blockage in the flue requires clearing.