We may have found other answers which could help you.
Click here for Boiler Good Hot TapHot water comes and goes!?
Vaillant F22 fault?
how to fix water pressure its down at bottom of grey part?
how do I rectify the fault as detailed below?
Vaillant VCW-Sine18 T3WFH Lights but then goes off after 5 Min?
Vaillant vcw gb242 eh central heating problem?