How to mend Vaillant Vc 142 E

how do I rectify the fault as detailed below?

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

Why is heating on at night?

Valliant Eco tec 28?

Vaillant igniting issue ( domestic ) not CH?

Vaillant ecomax 828/2 e water pressure sensor?

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

Vaillant ecotec 831 plus?

vaillant ecoTEC plus boiler fault code - how to fix?

Boiler over pressure on the hot-water side?

Vaillant vcw gb242 eh central heating problem?

my vaillant boiler is saying a code com on it ?

Vailliant turbo max plus 824e?

how do I vent the heat exchanger?

What does f.25 mean?

Vaillant Ecotech Plus 831 F22 fault?

Vaillant 828E - no hot water?

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

Vaillant ecotec plus 630?

Valiant thermostat , BMU-Err ?

Vaillant Thermocompact Fault?

No hot water, intermittent when air temp drops?

Vaillant condensing boiler ecoTEC plus?

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

Problem with the pressure in combi boiler?

Hot water comes and goes!?

my boiler will no work?

Advice?

Vaillant F22 fault?

Vaillant eco plus 531 boiler?