What does the Vaillant Home F90 fault code mean?
The F90 fault code indicates a problem with the system thermostat in the Vaillant Home boiler. This typically means that the thermostat is not communicating correctly with the boiler, which can affect the heating performance.
Common Causes
- Faulty Thermostat: The thermostat may be malfunctioning or damaged, preventing it from accurately reading the temperature.
- Wiring Issues: There could be loose or damaged wiring connections between the thermostat and the boiler, disrupting communication.
Can I fix it myself? (DIY)
If you are comfortable with basic electrical work, you can check the wiring connections for any visible damage or looseness. However, for safety reasons, it is highly recommended to call a Gas Safe Engineer to diagnose and repair any gas or electrical issues.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for addressing the F90 fault is around £150 to £250. This includes the cost of a replacement thermostat and labour charges for a qualified engineer to install it.