Just a wild card guess, but could it be your
A/C servo unit gone psychO?
Don't know how to check it other than inspect
for leaks. 1980 was last year with this
muck device. Assuming your vehicle was included.
good luck.
aside: that's why bench seats were engineered.
(girl friend)

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1979 300D
133K miles
1989 300SE
1995 C280