my "new" 1984 190D does the same thing. I just got it a week ago and the AC seemes to cycle often. It's been converted to R-134. I havn't had the car long enough to really get a good feel for how the AC works.

I do notice that the center vents and side vents temps never match. Center is always cooler than the sides. Even when I have the temp turned warmer or the AC off in the economy mode.

I have noticed a vacuum leak in the trunk lid, for the trunk lock I asssume. But all the door locks, truck & gas lid locks work.

But the Trans likes to shift to 1st or 2nd and stay there much too long when accelerating before going straight to 4th, rarely shifting thru 3rd. Very annoying but I assume with all the vacuum systems inter-related (trans, AC, locks) that I will be chasing these problems for a while.

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1987 300TDT
1981 VW MKI Caddy 1.6 diesel, waiting on engine swap
1983 D-50 Power Ram 4x4 "Mitsubishi" 2.3 turbo diesel
assorted gas powered crap and motorcycles

RIP: 1984 300TDT, 1982 300TDT, 1984 190D 2.2, 1992 300D 2.5, 1987 300TDT, 1982 Maxima LD28, 1983 Maxima LD28, Isuzu C223 P'ups X3, 1983 Holiday Rambler 6.2 Banks turbo diesel, 1984 Winnebago LeSharo 2.1 TD, 1985 Allegro 6.5