How to mend Vaillant Ecotech Plus 428

my vaillant boiler is saying a code com on it ?

Valiant thermostat , BMU-Err ?

Vaillant Ecotech Plus 831 F22 fault?

Vaillant vcw gb242 eh central heating problem?

my boiler will no work?

Vailliant turbo max plus 824e?

Problem with the pressure in combi boiler?

No hot water, intermittent when air temp drops?

Vaillant eco plus 531 boiler?

can i replace my Potterton EP2 2 way programmer with a Center EHE0200361 RF?

Vaillant condensing boiler ecoTEC plus?

how to fix water pressure its down at bottom of grey part?

vaillant ecoTEC plus boiler fault code - how to fix?

Advice?

how do I rectify the fault as detailed below?

how do I vent the heat exchanger?

Vaillant ecotec 831 plus?

Vaillant F22 fault?

What does f.25 mean?

Vaillant Thermocompact Fault?

Vaillant 828E - no hot water?

Vaillant VCW-Sine18 T3WFH Lights but then goes off after 5 Min?

Vaillant igniting issue ( domestic ) not CH?

Vaillant ecotec plus 630?

Boiler over pressure on the hot-water side?

Hot water comes and goes!?

Why is heating on at night?

How do I fix f22 error on my Vaillent Ecotec Plus boiler?

Valliant Eco tec 28?

Vaillant ecomax 828/2 e water pressure sensor?