Viessmann F1 Fault Code – Likely Causes, And Possible Fixes

October 17, 2022

What Is the Viessmann F1 Fault Code?

The Viessmann F1 fault code is a safety feature across the Viessmann boiler range, including the Vitodens 100-w and 050-w combi boilers.

It is very similar to the F0 fault and indicates that the boiler has detected a high temperature and has stopped the burner from igniting until the temperature has decreased.


Common Causes of The F1 Fault

The F1 fault is usually caused by low water pressure inside the boiler, meaning the temperature gets too high and the boiler goes to a lock-out state to prevent further damage.

It can also be caused an airlock in the heating system, a faulty pump, a corroded system, or a blocked heat exchanger.


If I Reset My Boiler, Will This Fix the F1 Fault?

When the boiler has cooled down enough resting your appliance will start the ignition process again. Sometimes the boiler will work for a short period, this is however unadvisable as the boiler has locked out due to excessive temperatures, and the possibility of causing further damage remains.


Can I Fix the F1 Fault Myself?

The Viessmann F1 fault can be caused by many different issues, eventually, all of them will need an experienced gas-safe registered heating engineer to properly diagnose the root cause and complete a boiler repair.

If the fault is caused by low pressure, or air in the system you can re-fill the boiler or bleed the radiators and that should get the boiler working again for a while.

If the pump or sensors inside the boiler are faulty, you’ll need to call a Gas Safe professional to safely repair the boiler.

If the main heat exchanger is blocked it will be a very costly and time-consuming repair, you might it find it more cost-effective to have a boiler replacement.



The Viessmann F1 fault indicates a potentially serious safety issue that should be investigated a Gas Safe registered heating engineer.

It might reset, but this not recommended because you could cause more damage and end up needing to replace the whole boiler, as a pose to just a part.

Often the issue is low pressure, and this can be repaired without a pro. However, there are many reasons your boiler will display F1 and the issue should be inspected, even if it does reset.

Heatsy are Viessmann trained, DBS cleared, and Trading Standard approved heating contractors. We specialise in domestic heating boiler repairs, Gas Safe number 648547.

We hope you found this article interesting and useful, if you didn’t please let us know why and what we could do to improve it.

If you did please share so that other people can benefit from it too, you can also follow us on social media to get other useful content as it’s publish or sign up to this blog to get the content delivered straight to your inbox.

Please remember, we’re heating experts so if you need your boiler repaired, a new heating installation or if you’re struggling with anything we’ve discussed here feel free to get in touch with us now so we can see how our solutions might help you.

Thank you for reading.