A/C problem

[mvaneersel]

My 98 Sentra just started doing this: The engine surges with a tick/clunck when the a/c is on. The clunck is every 1-2 seconds or so. The a/c still works but it does not seem to be working as well as it should. That is a change. The engine also dies in idle now, only with the ac on, although I can keep it running with my foot on the accelerator a bit.
So, is this:the clutch, the compressor, the belt, the bearing? All of the above? Depleted system? Could it be the alternator?
Any ideas??

Thanks!