Air conditioning not working

[Lukes]

Hi I'm a Newby on here. I have a vw passat 2013 estate 2lit this.
My air con stopped working at the end of last summer and I didn't both to get it ready gassed until yesterday, it had never been done before. It was low on gas but it still doesn't work, i was told thathat the compressor was not kicking in. I am a retired electronic engineer, well used to reading circuit diagrams but I'm afraid the one in the Haines manual has beaten me. Can someone help put me on the right track please. It looks like the air connection switch will pull in a relay and then energise some sort of solo I'd on the compressor. I also understand that there is a pressure switch in series with this circuit which monitors the gas pressure. It would be really helpful to me to confirm the above and give me some guidance, maybe a photograph of the location of these things, I'm told that pressure switch is a very comm on problem.

Roger