What does the Vaillant ecoTEC exclusive F43 fault code mean?
The F43 fault code on a Vaillant ecoTEC exclusive boiler indicates a problem with the expansion vessel, which is responsible for maintaining system pressure and accommodating thermal expansion of water. A faulty expansion vessel can lead to pressure fluctuations and potential system failure.
Common Causes
- Loss of Pre-charge Pressure: The air pressure inside the expansion vessel may have dropped, preventing it from functioning correctly.
- Physical Damage: The expansion vessel may have developed a leak or other physical damage, leading to failure.
Can I fix it myself? (DIY)
It is advisable to call a Gas Safe Engineer to address this issue, as working on gas appliances can be dangerous. Attempting to fix the expansion vessel without proper training may lead to further complications.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for replacing a faulty expansion vessel on a Vaillant ecoTEC exclusive boiler is around £250. This includes the cost of the part and labour, reflecting the complexity of the job and the need for a qualified engineer.