While you wait for answers, we may have found some information which could help you.
Click here for Heating Pressure RadiatorsVaillant F22 fault?
how to fix water pressure its down at bottom of grey part?
Vaillant ecotec 831 plus?
Vaillant 828E - no hot water?
Vaillant VCW-Sine18 T3WFH Lights but then goes off after 5 Min?
Vailliant turbo max plus 824e?