What does the Vaillant ecoTEC plus F78 fault code mean?
The F78 fault code on the Vaillant ecoTEC plus indicates that there are faulty system parameters, which may affect the boiler’s operation. This can be due to incorrect settings or a malfunction in the control system.
Common Causes
- Incorrect Configuration: The boiler may have been improperly set up during installation or maintenance, leading to parameter mismatches.
- Faulty Control Board: A malfunctioning control board can cause the system to read parameters incorrectly, triggering the F78 fault.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for this fault, as it involves system parameters that require professional diagnosis and repair. Attempting to fix it yourself may lead to further issues or safety hazards.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving the F78 fault could be around £150 to £300, depending on whether a control board replacement is needed. This cost reflects the complexity of diagnosing and fixing parameter issues.