We may have found other answers which could help you.
Click here for Boiler Combi Faulthow to fix water pressure its down at bottom of grey part?
Vaillant 828E - no hot water?
Vaillant vcw gb242 eh central heating problem?
Vaillant VCW-Sine18 T3WFH Lights but then goes off after 5 Min?
Advice?
Problem with the pressure in combi boiler?