How to mend Vaillant 835/e2

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my boiler will no work?

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Boiler over pressure on the hot-water side?

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

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Advice?

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

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

Why is heating on at night?

vaillant ecoTEC plus boiler fault code - how to fix?

Problem with the pressure in combi boiler?

Vaillant Thermocompact Fault?

No hot water, intermittent when air temp drops?

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

Hot water comes and goes!?

how do I vent the heat exchanger?

how do I rectify the fault as detailed below?