I remember seeing a thread here about this a while back. I believe there is a stepper motor located under there somewhere that can go bad. It actuates dampers or air doors for the AC. If you do a search you will probably find it easily because it was discussed not more than a month ago.


Edit: Here you go:

http://www.peachparts.com/shopforum/showthread.php?t=212467&highlight=stepper

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Bob in Richmond

'97 S320 (LWB), Ruby Red Metallic, 73k miles
'97 S420V, Smoke Silver Metallic, 155k miles