I converted an automatic to manual system on a 116 (1980 300SD). Not according to the manual, but it sure works. When I want heat or A/C I can get either.

I think I posted how I did it earlier. Just do a search to find it. BTW, I use the existing vacuum system for the vents since there are manual open/close ones on the 116 in the dash.

Rev. Dr. G.