We may have found other answers which could help you.
Click here for Heating Valve Vaillant
Vaillant ecotec 831 plus?
Vaillant 828E - no hot water?
Vaillant VCW-Sine18 T3WFH Lights but then goes off after 5 Min?
Problem with the pressure in combi boiler?
Vaillant eco plus 531 boiler?
how do I rectify the fault as detailed below?