Re: 2000 CV - AC Problems??
I should expand on what I wrote early this morning. I wrote the text during a quick coffee break I took during an all night thrash (not a Ford this time, but a CRF450X) in the shop, and it was a little brief.
What you are possibly experiencing is called belt "wrap-up" Physics majors will be all over me, but I think the belt loads increase X RPMs squared. When the AC clutch engages at higher engine speeds, the belt is under tremendous load and it tries to "walk" or wrap, around the pulley. And it will if the tension is low, such as with a worn tension spring as I described in my first post. The vibration you are feeling are the oscillations caused as the belt, and any loose components driven by the belt, "un-wrap".
As Bert said, open the hood and see what's happening. Pay close attention to the idler pulley/tension pulley, then check for loose components.
Remember to never stand in line with any rotating belt or accessory while the eng is running.