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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 01-17-2013, 04:41 PM
BoofyBlitzed BoofyBlitzed is offline
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Location: Washington
 
Join Date: Jan 2013
Posts: 1
Mein Auto: 1999 323i
Replaced Alternator???

I replaced my alternator this week and when i started my car my battery light was on. I checked the voltage at the post on the back of the alternator and it was only 12 volts when i first started the car and the more i ran it the lower it got. I checked the pulley and it was turning fine, and i have a brand new battery. the only thing i can think of is that i got a bad alternator from Napa?!?! any other ideas? I'd rather not yard out the alternator again just to find out its not the problem.

thanks for the help
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  #2  
Old 01-17-2013, 04:46 PM
QAfred QAfred is offline
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Location: Panhandle of Florida
 
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Posts: 919
Mein Auto: 328i, 330ci, R1200C
You should have 12.4 to 12.6 volts on your battery with engine off or your battery is not fully charged. You should have 13.6 to 14.0 volts once you start the car.

Check the voltage at your battery post, check all chassis grounds too. If they are good make sure you do not have parasitic drain/ a short somewhere pulling all the voltage to ground.

Last edited by QAfred; 01-17-2013 at 04:48 PM.
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  #3  
Old 01-17-2013, 05:02 PM
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bluebee bluebee is offline
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Location: San Jose, California
 
Join Date: Mar 2008
Posts: 21,279
Mein Auto: 02 BMW 525i M54 auto 130K
You have to start over on the diagnostics:
- DIY how to test a BMW battery & alternator
__________________
Each repair should invariably add to our knowledge base by the process of inexorable incrementalism.
Your job, in return, is to read the suggested threads, where the best people will always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #4  
Old 01-17-2013, 09:16 PM
jmo69 jmo69 is offline
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Location: Eastern Wisconsin
 
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Posts: 170
Mein Auto: 98 328is 2003 325xi
I feel your pain about removing the alternator again. I had to replace a new one I got from Advance because the bearing was bad. Take it out and have them test it, the weird thing about mine was the battery light never came on, even with the voltage low enough for the car to not crank.
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  #5  
Old 01-18-2013, 05:42 AM
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bluebee bluebee is offline
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Location: San Jose, California
 
Join Date: Mar 2008
Posts: 21,279
Mein Auto: 02 BMW 525i M54 auto 130K
Quote:
Originally Posted by jmo69 View Post
the weird thing about mine was the battery light never came on, even with the voltage low enough for the car to not crank.
Same thing happened to me.

By the time the battery light came on, the car had already died in the middle of the road.

Full details (as always) here:
- One users' example of total electrical failure (AAA towed away) alternator repair (1)
[Read post #66 & post #107 & especially post #146 for M54 DIYs]
__________________
Each repair should invariably add to our knowledge base by the process of inexorable incrementalism.
Your job, in return, is to read the suggested threads, where the best people will always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #6  
Old 01-18-2013, 10:16 PM
GoForthFast GoForthFast is offline
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Mein Auto: '04 330Ci 6-speed
Don't care where you got the alternator from, but Bosch or Valeo replacement is a must. Anything else is going to fail faster.

Last edited by GoForthFast; 01-19-2013 at 11:11 PM.
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