Vaillant Combi Boiler

Vaillant combi boiler models, guide, comparison, parts, manual, drawings, help

Boiler showing F.25


Our boiler is 9 years old, seemed fine but the other day it showed a message of F.25 and now heating won’t come on and hot water only goes for a little bit.

I have looked on your website and it says it would be the water switch as the water pressure is too low, so looked on the display and it does look low. Showing 0.6 bars .

How can I get this fixed?

Thank you.



Hi Steven,

This really depends on the boiler model you have.  For Ecotec Plus the F.25 Fault refers to safety shut-off function.  We have explained the cause and solution in a previous FAQ here.

For Ecotec Pro the F.25 fault refers to a problem with the compact thermal module cable harness.  This means that the cable harness is broken and requires replacing.


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