I really appreciate the info that you have provided!!! That noise is driving me crazy and I'm going to follow your instructions on cleaning the servo. Thanks!!!
I followed the instructions and removed the servo.
The "gerbil" noise still persists despite disconnecting this servo that was perviously described -- Btw, this servo controls the mode change. So, I listened in and dug in further by removing the white venting conduct, I traced down to a 2nd servo that was really the noise maker, at least for my wife's RX300. This 2nd black servo which seems to control the temperature, since it reacts to my change of temperature as I moved from HOT to COLD and back, is located directly below the 1st servo that controls mode change. The mounting screws for this 2nd servo is hidden behind two silver metal tube that was heated up and had burned me several times when I removed the 1st servo. I gave up trying to remove this 2nd servo to perform the cleaning described earlier since it's late and dark in the evening working under only a pair of garage outside lamps plus emergency power pack lighting. Perhaps a 2nd attempt some time in the future. Thanks for your valuable insight to this.
This vehicle is at 121,000 miles and had this noise problem for at least 30,000 miles. Btw, I just had a blown transmission (car ceased to move in ALL gears) and took it to the local AAMCO specialist to rebuild it for $3600 (incl tax). It was jerking a bit and the engine tends to stall initially. But after driving for some 200 miles, all the initial problem went away as AAMCO guidelines had claimed and the car is now good as new -- transmission wise -- came with a 3 year or 50,000 miles warranty. Now trying to work through a wheel alignment problem...