We may have found other answers which could help you.
Click here for Help Error Hot Water BoilerWhat does f.25 mean?
Vaillant eco plus 531 boiler?
vaillant ecoTEC plus boiler fault code - how to fix?
Vaillant ecotec 831 plus?
Vaillant VCW-Sine18 T3WFH Lights but then goes off after 5 Min?
Vaillant 828E - no hot water?