How to mend Vaillant Ecotec 618 R1

my vaillant boiler is saying a code com on it ?

Hot water comes and goes!?

Vaillant 828E - no hot water?

What does f.25 mean?

Why is heating on at night?

Vaillant igniting issue ( domestic ) not CH?

how do I vent the heat exchanger?

Vaillant ecotec 831 plus?

Boiler over pressure on the hot-water side?

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

No hot water, intermittent when air temp drops?

Vaillant Ecotech Plus 831 F22 fault?

vaillant ecoTEC plus boiler fault code - how to fix?

how do I rectify the fault as detailed below?

Vaillant ecomax 828/2 e water pressure sensor?

Vaillant vcw gb242 eh central heating problem?

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

Advice?

Vaillant Thermocompact Fault?

Valiant thermostat , BMU-Err ?

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

Vailliant turbo max plus 824e?

Valliant Eco tec 28?

Vaillant eco plus 531 boiler?

Vaillant F22 fault?

my boiler will no work?

Problem with the pressure in combi boiler?

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

Vaillant condensing boiler ecoTEC plus?

Vaillant ecotec plus 630?