The owner's manual has a detailed description of the climate control system; as I no longer own a 123, I can't post pictures. You might be able to find the owner's manual in pdf somewhere in the forum or elsewhere on the web or (heaven forbid!) actually buy a copy on eBay or books4cars.com.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970