I have a 2000 S70 GLT (automatic with turbo) and from day-one, I have had this 'problem'. At the time, I was living in Houston and brought it to the dealer there. They removed the glove box, checked for leaks (but found none). They added some special dye to determine if a leak occured over time. They never found a leak and the AC has always felt very cold. Too cold, in fact! BTW, I never keep my AC on the AUTO setting and keep the vents open as much as possible to prevent mold build-up within the vehicle/vents.

I had a similar problem in a previous vehicle (1993 Mitsubishi Presis). This was a manual 4 cylinder transmission. That clicking noise must have occured every 10 seconds while driving at highway speed. It drove me nuts (no pun intended). The dealer checked this 'problem' repeatedly and said it was normal and found no leaks (there was never a problem with the AC running too cold in that car either). The dealer told me it occured because the engine was so small. Perhaps this occurs in 4 cylinder and 5 cylinder vehicles above a certain weight?

As long as you have this 'problem' on dealer record, you should be ok when/if your warranty runs out, right?

See you 'clicking' down the highway!