Air-Con Problem

[crazychick]

Please any advice is greatly appreciated, i have a 2002 C-Max...using the car over a year, i noticed the air-con wasnt as cold as it could be but i just thought it was due a service, then typically packs up, with a car full of people on a hot day!!! So i booked into Garage to be told its not a service that is required but an Air-Con Compressor, but i have been told there is power getting to it....now im not clued up on the above, if it has power surely it is working, is it a sealed unit or is there a quick fix or cheaper fix please please help! I have dual climate if this make a difference

[FOCA]

The aircon compressor pump runs off a a pully from the crank and is switched on with an elecromagnetic clutch

its a realatively complicated system - here is a simplified explaination -

http://www.airconcars.com/html/how_it_works.html

its got cold in the UK now so if i still had AC (stripped out for better performance/ economy) i would not be using it again untill at least March/April and more likely June, there were a handful of days i missed it though