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Old 05-05-2011, 02:28 PM
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benhogan benhogan is offline
CPA/Greasemonkey
 
Join Date: Aug 2009
Location: Chapel Hill
Posts: 1,092
Quote:
Originally Posted by sedna322 View Post
I have a 1984 mercedes 300D (European) I have had some problems with my battery lately. It seems like the alternator is not charging the battery. It will be running fine, and then out of no where it won't start. The first time it has happened I thought it was just that the battery had died, but then after getting a new battery it died again about three weeks later. I got a new battery again and the same thing happened again. I am not really sure what is going on. If anyone has any idea please let me know.
use a multimeter in the 2-20volt setting to do this test--

test the voltage across the two terminals on the battery.

-with the car not running, the voltage should be exactly 12.6volts (6 cells at 2.1 volts per cell)

-with the car idling, the voltage should be in the 13 volt range (anywhere 13.xx volts is good)

-with the card idling, turn on the headlights, the voltage should not be BELOW 12.6 volts, if that is the case then the alternator is not charging

- if the voltage goes above, say, 14.3 volts at any time then the alternator is overcharging (equally bad)
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1987 190d 2.5Turbo
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