1982 300SD. Only way to get heat to the floor is by pushing button B. (two white arrows) If button C or D is pushed, leg flap door slowly closes. Starting from right side button E. Push button D and heat comes out left and right vents and defroster vents, nothing to floor. Button C, same thing, except AC pump runs. Have replaced temperature regulator, climate control unit in dash, and have gone through all the trouble shooting chapters in the manuel, and can find nothing showing the problem I have. I also went through the online manuels looking for an answer, and could find nothing. fg

I'd suspect one of the switchover valves behind the climate control buttons. Sounds like it's not keep vacuum on the footwell pod. I'm not familar with the system on the SD's, so it's possible you don't have switchover valves.

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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

Yes, the SD has the vacuum switchover valves with lots and lots of vacuum hoses. If one of the switches is bad, why does one button, (the one with two white arrows, shown as button b on the manuel's pictures) put heat down to the floor?? fg