We may have found other answers which could help you.
Click here for Sparks Light GasVaillant ecotec 831 plus?
how to fix water pressure its down at bottom of grey part?
Vaillant F22 fault?
Vaillant 828E - no hot water?
Vaillant condensing boiler ecoTEC plus?
Vaillant VCW-Sine18 T3WFH Lights but then goes off after 5 Min?