Welcome to Bimmerfest -- The #1 Online Community for BMW related information! Please enjoy the discussion forums below and share your experiences with the 200,000 current, new and past BMW owners. The forums are broken out by car model and into other special interest sections such as BMW European Delivery and a special forum to voice your questions to the many BMW dealers on the site to assist our members!

Please follow the links below to help get you started!

Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

Reply
 
Thread Tools Display Modes
  #1  
Old 01-02-2013, 12:32 PM
necero necero is offline
Registered User
Location: Chicago, IL
 
Join Date: Jan 2013
Posts: 14
Mein Auto: 2000 BMW 540i
Bad alternator or battery?

Hi everyone, looking for some input. I've got a 2000 540i with ~125k miles on it. Here's the deal:

Went out to dinner on the 31st, valet left my lights on and the car died. Jump started it and my battery light was going on/off depending on how hard I was accelerating. Got home to check the battery and the "magic eye" was black, meaning it needed a charge. I was able to drive ~80 miles with the battery light issue still going on. Under acceleration the light would go off and the dash/radio lights would brighten a bit.

I had it charge overnight and the magic eye was still not showing a full charge. Using test #9 it showed a voltage of 10.2 when the car was off, and it dropped to 8.9 at idle.

At work today the car needed to be jumped to start. To see if it could possibly be an alternator issue I let the car sit idle for about 20 minutes and it died, leading me to believe that the alternator wasn't charging the battery. I'm not sure if this would be due to a faulty alternator or if a bad cell could cause the battery to not charge (I read something along those lines in some other places).

I had the alternator replaced about 4 months ago. I don't know if it's just another bad alternator or if the battery is shot now. Any help would be much appreciated.
Reply With Quote
Ads by Google
  #2  
Old 01-02-2013, 02:07 PM
edjack edjack is offline
Officially Welcomed to the 'Fest
Location: San Jose, CA
 
Join Date: May 2007
Posts: 8,846
Mein Auto: '97 540i 6 speed
Simple alt test: run engine at 1000 RPM. If the voltage does not rise to at least 13.5 V. the alt may be bad. A proper alt test should be run.

After charging overnight, and setting a few hours, battery voltage s/b 12.5+

If the battery is more than 5-6 years old, it may be on the way out. Sounds like there is one dead cell. Have it load-tested.
__________________


Ed in San Jose '97 540i 6 speed aspensilber over aubergine leather. Build date 3/97. Golden Gate Chapter BMW CCA Nr 62319.

Last edited by edjack; 01-02-2013 at 02:10 PM.
Reply With Quote
  #3  
Old 01-02-2013, 02:13 PM
necero necero is offline
Registered User
Location: Chicago, IL
 
Join Date: Jan 2013
Posts: 14
Mein Auto: 2000 BMW 540i
Quote:
Originally Posted by edjack View Post
Simple alt test: run engine at 1000 RPM. If the voltage does not rise to at least 13.5 V. the alt may be bad.

After charging overnight, and setting a few hours, battery voltage s/b 12.5+
Thanks a lot, I will try that. I just replaced the battery with a new one. It was at 12.1 volts when the car was off and dipped to 11.2 during idle. The battery light issue was the same, light was on during idle and went off under acceleration.

Last edited by necero; 01-03-2013 at 08:39 AM.
Reply With Quote
  #4  
Old 01-02-2013, 04:57 PM
Spokane540ia Spokane540ia is offline
I need to replace what?
Location: Spokane, Wa
 
Join Date: Jul 2008
Posts: 430
Mein Auto: 2002 540i
Sounds like your alternator is bad, and that may have killed your battery, too. It happened to me. The "battery" light going on and off could also be a slipping belt.

Hope that helps
__________________
Reply With Quote
  #5  
Old 01-02-2013, 11:40 PM
mjalloul11's Avatar
mjalloul11 mjalloul11 is offline
Officially Welcomed to the 'Fest
Location: Lebanon
 
Join Date: Apr 2012
Posts: 685
Mein Auto: 1996 528i 1999 MB c240
It looks like your alternator is not charging, could be the carbon brushes inside it are worn or a slipping belt.
Reply With Quote
  #6  
Old 01-03-2013, 03:00 AM
JimLev JimLev is offline
Officially Welcomed to the 'Fest
Location: MA
 
Join Date: Dec 2003
Posts: 3,617
Mein Auto: 540/6, S60 Volvo, Tribeca
You said you charged battery overnight, what type of charger did you use. Was it a 2 amp charger or a 10 amp charger? A 2 amp charger will require two days to charge the battery if it was dead.
Was your spare battery fully charged when you installed it?
Your alternator is water cooled and doesn't have carbon brushes in it.
If it was replaced 4 months ago it should be under warranty, take it back and have them check it out after you determine if the battery is good or bad.
__________________

2000 540/6 Slightly tweeked...everywhere
Reply With Quote
  #7  
Old 01-03-2013, 06:10 AM
flyboyy's Avatar
flyboyy flyboyy is offline
I glow in the dark
Location: Gotham City
 
Join Date: Jun 2006
Posts: 578
Mein Auto: 2003 BMW 530i
simple test... when car is off use a multimeter and check what voltage you got on the battery.

it should be 12v or so

and then turn on your car and test the battery again with voltage meter.. you should be reading 13.5+ Volts or more.. it should not past 14.5 ... the job of the alternator is to charge the battery up .. without under charging it or over charging it...

in my case when I had a bad alternator .. when I started car.. my battery was 18V it was over charging the battery therefore killing it.

hope this helps.
Reply With Quote
  #8  
Old 01-03-2013, 06:22 AM
bluebee's Avatar
bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
 
Join Date: Mar 2008
Posts: 20,349
Mein Auto: 02 BMW 525i M54 auto 130K
- Complete DIY for how to test a BMW battery & alternator (1) & a diagnostic procedure to test for overnight parasitic battery drain (1) & how to find all the fuses (1) & how to choose a good aftermarket battery (1) and a simple battery replacement DIY (1) & where to find the battery explosive charge emergency quick disconnect (1) (2)
__________________
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
Reply With Quote
  #9  
Old 01-03-2013, 08:03 AM
necero necero is offline
Registered User
Location: Chicago, IL
 
Join Date: Jan 2013
Posts: 14
Mein Auto: 2000 BMW 540i
Quote:
Originally Posted by JimLev View Post
You said you charged battery overnight, what type of charger did you use. Was it a 2 amp charger or a 10 amp charger? A 2 amp charger will require two days to charge the battery if it was dead.
Was your spare battery fully charged when you installed it?
Your alternator is water cooled and doesn't have carbon brushes in it.
If it was replaced 4 months ago it should be under warranty, take it back and have them check it out after you determine if the battery is good or bad.
Thanks for everybody's help. To answer your questions:

It was a 10 amp charger. The battery was from 2007 so it needed to be replaced at some point anyway. The replacement battery is brand new and fully charged.

The alternator is under warranty still, I'm just trying to see if there could be anything else causing the problems because it's a huge pain getting it out.

I have been reading elsewhere and it has also been suggested here that it could be a belt/tensioner issue. It makes sense to me (which probably means I'm wrong) that it could be an issue there since the light goes off under acceleration and the OBC shows the voltage at 13.5. At cruising speed/idle the light is on and the voltage is around 11.5. Does that seem logical?

Again, I appreciate all the advice from everybody.
Reply With Quote
  #10  
Old 01-03-2013, 08:23 AM
Fudman's Avatar
Fudman Fudman is online now
Officially Welcomed to the 'Fest
Location: Sudbury, MA
 
Join Date: Apr 2007
Posts: 6,155
Mein Auto: '02 530i Sport auto
It could be any of those things as the OBC voltage output should be constant, irregardless of engine rpm and your seems to be fluctuating with rpm. Slipping belts is fairly rare. I am guessing it might be your voltage regulator as that is the function of the VR. Perform the tests in BlueBee's post to determine what is failing.

And make sure your battery connections are nice and tight.
Reply With Quote
Reply

Bookmarks


Forum Navigation
Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)
Today's Posts Search
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On



Forum Jump


All times are GMT -7. The time now is 07:45 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
© 2001-2011 performanceIX, Inc. All Rights Reserved .: guidelines .:. privacy .:. terms