W210 air con compressor clutch doesn't work (fixed by SD C4)

(quoted from http://www.mbclub.co.uk/forums )
My is 2002 e320cdi. This morning I got air condition regassed. And I noticed while ot was being done that the compressor clutch isn't working - so I have no air condition she has manual air condition with knows. The EC button works, well the light cones on! I'm hoping it's not the compressor and hopefully just relay or switch, but where us the relay located? And is there any common faults I should be looking for. I've only had the car a month so unsure if wasn't working for long time, I just hoped it was low gas!

Get the AC codes read. This will help with diagnosis. STAR diagnostic tool will read all fault codes. If it was the auto climate control (digital) version, it can read it's own fault codes. The plug-and-play bundle--- SD C4 with Dell D630 laptop will be a good choice to meet your urgent need for the newest 2015.7 SD Connect Compact 4 software will be pre-installed before delivery and you can use it directly when you get it.
You can learn more about the Star diagnosis sd connect compact 4 with dell d630 from http://www.MBStarTool.com/wholesale/-sd-connect-compact-4-star-diagnosis-dell-d630-laptop.html. starshop is a pretty professional website specialized for vehicles.