Yea, the early alternators had a hard enough time keeping up with all the electrical users with A/C on. If we are talking about the 82 300D, then I suspect a motor mount problem as your vibrations. The motor idles slower with the A/C and this accentuates a poor mount situation.
Your car doesn't have the compressor control relay and will burn the belt up if the A/C is left turned on and the compressor seizes.
Bosch Master, ASE Master, L1
33 years MB technician