I just joined this site so I could reply to this post and access the attachment posted above. I have owned a 1999 RX300 since February 2002. Have had that clicking sound directly behind the radio part of the dash intermittently for years. It would never make the sound at the dealer and I never found an answer. Thank you all. The only thing I'm not sure about is whether it only makes the noise when the AC is on. I don't believe that's the case so I presume it's the air mix servo. It's been probably seven years and now I know!
