If the 116 is like the 123, when the center vent pod goes bad it defaults to full defrost. Although I have 3 116 cars, I can not verify that they are simular.

Try a search for "center vents".

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1980 300SD Manganese Brown Metallic Clearcoat 248k
1979 300SD White 148 k
1984 300D Silver project car for daughter
1982 300D wrecked
1980 300SD 310K not running