How to mend Vaillant Vcw Gb 242 E H

my vaillant boiler is saying a code com on it ?

Hot water comes and goes!?

No hot water, intermittent when air temp drops?

how do I rectify the fault as detailed below?

Valliant Eco tec 28?

Vailliant turbo max plus 824e?

Why is heating on at night?

Valiant thermostat , BMU-Err ?

Vaillant condensing boiler ecoTEC plus?

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

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

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

Advice?

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What does f.25 mean?

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my boiler will no work?

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how do I vent the heat exchanger?

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

Vaillant vcw gb242 eh central heating problem?

Boiler over pressure on the hot-water side?

Vaillant eco plus 531 boiler?