Hi I have a 84' 300d, owned it for 5 years now, headache free till about the last 6 months.
one day car cranked over slowly but did start, but next day it was dead. Got a new battery and it lasted about a month and went dead. Got a new alternator, worked for a week- boom went dead, finaly got a suggested bosch alternator worked for 2 weeks and battery now dead again. Car always starts with a jump but the battery is just not holding charge or alternator keeps failing. Car is now in the shop but have a feeling they dont know what to look for??? A few people suggested a short or bad starter or some kind of power drain but who knows ??? Any tips or suggestions would be greatly appreiciated. thanx, mark

 

Talked to my mechanic, he claims the alternator he put in 2 weeks ago is bad. Of course he will cover the new one, but now this is 3 bad alternators in the last year.

Can something be blowing theese alternators or did I just hit a unlucky streak of bad ones ?

thanx, mark

 

Proper belt tension is critical in this car. If thebelt is evena little loose you won't generate enough electricity to keep the battery charged, especially if you're using accessories or driving at night with the lights on. One thing to check is the upper alternator bracket tensioner as they have been known to "break off" due to metal fatigue.

 

Thanx , Good point but still dont know how 3 alternators went bad in less than a year.

 

Sounds like you have a short draining the battery. Is the trunk lite/glove compartment litestaying on?

A bad battery will kill the rectifier in a good alternator in a matter of weeks. My experience has been that people will milk a dying battery to save a couple bucks not knowing that the alternator is being sacrificed to compensate for the low system voltage.

 

Do you honestly believe that three alternators went bad in less thana year?

 

I had a similar problem on my 240D except the alternator light would flicker intermittantly and after about a month the car would not start. After 2 alternators I found that the plug that goes in the back of the alternator was the problem. To fix it all I did was slightly twisted the pins on the alternator and forced the plug back in. Been 2 years now without a problem.