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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check to see if your alternator is charging the batt. also check your connections, make sure they are clean. and check the voltage regulator

__________________
hum.....
1987 300TD 311,000M Stolen. Presumed destroyed

Beatrice,
Welcome to the forum !!
Hope you get all the help you need & and enjoy your car !!
Reconnecting anything back is always going to have a bad outcome unless you know why it was disconnected. Best you disconnect it again & start on a proper check on the electrical system.
There are many threads on here about charging/battery problems. Best you do a little reading.
If you have a multi meter you can test to see if there is a discharge when everything is off.
For now, I would be removing one of the battery terminal leads when the car is left for any time not running. This will save your battery.

Good Luck !!!

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving