I would begin by plugging the green line that feeds the whole climate control system and confirm that the car shuts off fine with the climate control system completely out of the loop. If it does, I'd then move on to the various components of the ACC system, plugging lines to see if it solves the problem.

__________________
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