Doesn't sound to me like a short, more like a loose alternator belt or weak charging. What is the cold cranking amps of the battery and reserve capacity? I ask because you might have purchased the wrong type for a diesel.

__________________
81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.