What does the Viessmann Vitodens 100-W F42 fault code mean?
The F42 fault code indicates a problem with the air pressure switch in the Viessmann Vitodens 100-W boiler. This switch is crucial for ensuring that the boiler operates safely by monitoring the airflow necessary for combustion.
Common Causes
- Blocked Flue: A blockage in the flue system can prevent proper airflow, causing the air pressure switch to fail.
- Faulty Air Pressure Switch: The switch itself may be defective or malfunctioning, leading to incorrect readings and triggering the fault code.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer to diagnose and repair the issue, as working with gas appliances can be dangerous. Attempting to fix the air pressure switch or related components without proper training may lead to safety hazards.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for the F42 fault code is around £150 to £250, which includes the replacement of the air pressure switch and any necessary labour. This cost reflects the price of the part and the expertise required for safe installation.