UrS4 serpentine belt chirping, A/C compressor noise and rattle

[RJA]

I have a squeak in my '93 S4 serpentine belt that sounds a lot like a
cricket chirp.  Noise appears after engine has been warmed up, not present
when engine is cold.  Spraying water on the belt temporarily quiets it down.
I hesitate to put any lubricant on the belt, I think the problem appeared
after I degreased the engine.  Any ideas, other than replace the belt?

I also have some other noises from that area when idling, there is a slight
rattle while bringing the idle speed up to about 1500 rpm.  I replaced the
serpentine tensioner, which cured a hugh rattle when engine was cold, so the
tensioner is now fine.  There is some play in the viscous fan bearing,
though when I hold the fan in place the rattle is still there.  BTW, is the
fan supposed to be running when the engine is cold?  The Bentley manual
calls for a "switch-on" temperature of 169F at the fan, what does that mean?
Mine runs all the time, regardless of temperature.

I'm also wondering if the rattle might originate from the A/C clutch
bearing.  The A/C compressor works fine but is pretty noisy, any experiences
in dealing with the A/C bearing and clutch?  Are they prone to noises like
that, what does it take to replace the A/C bearing?  How do I diagnose
what's going on with the compressor clutch and bearing?  Would it cause a
rattle, even with the compressor off?

Finally, I guess I can't eliminate the timing belt, idler pulley and water
pump as some of the noise.  I assume I can run the engine when the
serpentine belt is off and check the timing belt for correct tension and
make sure the noise does not originate there.  Timing belt was done 15K ago,
should be good.

All tips appreciated.  I've had the car for 1000 miles now, these noises
detract from an otherwise great engine and fantastic car!

-- Rich - CT
   '93 S4
   '90 200q
   '83 Coupe GT