Heater controls are vacuum operated. Don't ignore the ignition key problem, it can turn into a very significant problem. There are lots of threads on it. Window switches independent of vacuum. There are threads on how to clean them.
The are vacuum diagrams in the sticky threads.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13