How to mend Vaillant Leaking Heating

my vaillant boiler is saying a code com on it ?

Vaillant ecotec 831 plus?

my boiler will no work?

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

Valiant thermostat , BMU-Err ?

Why is heating on at night?

how do I vent the heat exchanger?

Hot water comes and goes!?

Vaillant Thermocompact Fault?

Vaillant vcw gb242 eh central heating problem?

Boiler over pressure on the hot-water side?

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

Problem with the pressure in combi boiler?

Vaillant eco plus 531 boiler?

vaillant ecoTEC plus boiler fault code - how to fix?

Vaillant ecomax 828/2 e water pressure sensor?

Vaillant ecotec plus 630?

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

how do I rectify the fault as detailed below?

Valliant Eco tec 28?

Advice?

No hot water, intermittent when air temp drops?

Vaillant F22 fault?

Vaillant condensing boiler ecoTEC plus?

Vaillant igniting issue ( domestic ) not CH?

Vaillant 828E - no hot water?

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

What does f.25 mean?

Vaillant Ecotech Plus 831 F22 fault?

Vailliant turbo max plus 824e?