Bought my 1979 300D recently. Told it needed new battery. Had to jump start everytime I wanted to get her going. Purchased new battery because the old battery would not hold a charge. Tightened up alternator charge belt (or whatever it is called). Started right up w/out the jump start for about a week. Then on the weekend I was working the radio and discovered the power cord wasn't plugged in (probably for good reason). I plugged it back in and it remained that way for a few days--later undoing this--, and now I am back to jump starting in order to get her going. Perhaps the radio is not related at all. How should I go about testing why my battery is draining? I hate that I spent $$ on new battery just to have it drained out. Your thoughts and advice are most welcome.

--1979 300D Mercedes (silver) "Beatrice" (my 1st MB, purchased September '10)

*Thanks Aquaticedge for the advice.
*Great advice layback40, and thanks for noticing my newcomer status. I am finding some really helpful reading now.


UPDATE: Last night I removed the alternator and took it to my local alternator/starter exchange for diagnosis. This I did after I ran a multimeter test--the battery was at 12v roughly and did not go up when the ignition was started (only went slightly down).

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