I've heard lots of cars make that clicking sound with the AC on. I think it has something to do with the compressor clutch.

Not to imply that you guys don't know where the sound is coming from, but one other possibility to consider is that it may be a rock or a screw or nail in the tire treads. It happens to me allt he time. If you only hear the clicking sound when the VX is in motion, then you should definitely check the tires on the right side. (check them all the way around, then move the VX a couple of feet and check it again to see if there was anything underneath. But if it makes the sound mostly at idle, then it's probably the AC.

Good luck diagnosing the sounds!