Thanks for the help, I finally found it! I had to pop out the long trim strip in the coin tray located below the passenger airbag. Behind it were 3 screws. Once removed, the coin tray, with the under dash panel came off. The sensor blower was tucked up next to the main blower, wrapped in foam with a thin metal bracket around the foam held in place with a single screw. I got it out and it was very dirty but when I hooked it up to 12 volts it did work. A combination of canned air, shop vac and electronics cleaner got it nice and clean. I put everything back together, did the "smoke test", as suggested, and the air seems to flow well.

Thanks for the great help!

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire