We may have found other answers which could help you.
Click here for Vcw H Heat Exchangervaillant ecoTEC plus boiler fault code - how to fix?
What does f.25 mean?
Vaillant 828E - no hot water?
how to fix water pressure its down at bottom of grey part?
Vaillant VCW-Sine18 T3WFH Lights but then goes off after 5 Min?
Hot water comes and goes!?