What does the Worcester Bosch Greenstar CDi F42 fault code mean?
The F42 fault code on the Worcester Bosch Greenstar CDi indicates a problem with the heat exchanger, which is crucial for transferring heat from the boiler to the water system. This fault can lead to reduced heating efficiency and may cause the boiler to shut down to prevent further damage.
Common Causes
- Blocked Heat Exchanger: Debris or limescale buildup can obstruct the flow of water, leading to overheating and triggering the fault code.
- Leaking Heat Exchanger: A physical crack or leak in the heat exchanger can cause a loss of pressure and efficiency, resulting in the F42 error.
Can I fix it myself? (DIY)
It is highly recommended to call a Gas Safe Engineer for this issue, as working on the heat exchanger involves gas and electrical components that require professional expertise. Attempting DIY repairs could be dangerous and may void your warranty.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for fixing the heat exchanger on a Worcester Bosch Greenstar CDi is around £600 to £800. This includes parts and labour, as the heat exchanger is a significant component that requires skilled installation.