BATTERY LIGHT IS ON - what to do?

**deilenberger** · Fri, Oct-29-2010, 03:07:44 AM

After checking the connection - you may as well go get a rebuilt one from BMW... what you're seeing is brush bouncing - the slip rings are probably out of round and/or the brushes are worn out and the springs aren't pushing them against the slip rings hard enough.

The "rebuilt" ones from Autozone would be better called "repainted" ones.. and since worn brushes are probably the biggest cause of failure, it's not a surprise that the ones you're getting are having problems. If you're real ambitious - take one to a local auto-electrical shop that does alternator rebuilds. They'll have a new regulator/brush assembly that just screws right in, and chances are good that will fix the problem.

MY02M3DINAN · Fri, Oct-29-2010, 01:29:15 PM

Quote:

Originally Posted by ZiMMie

OP check you power cable from the alternator to the starter. Also check the main connection at the boost point left side of the engine bay.

GREAT ideas... checked them both and they are OK.

The battery is only a couple years old and holds a charge very well.
I measure at least 12VDC after sitting overnight.

I'm going to check my battery connections again.... I've had problems in the past with a poor clamp. Maybe this is the cause?

Anyone know if the alternator is circuit breaker/fuse protected?
I recall old style headlights had an automatic resetting circuit breaker system that caused the headlights to blink when there was a short.

But If I still have problems, I'm taking the alternator to a local shop to be checked out.

Voltaire · Fri, Oct-29-2010, 01:33:34 PM

After reading about all the problems with Autozone alternators, I'd be inclined to go with one from BMW.

MY02M3DINAN · Fri, Oct-29-2010, 03:07:03 PM

Quote:

Originally Posted by Voltaire

After reading about all the problems with Autozone alternators, I'd be inclined to go with one from BMW.

Well, considering my factory alternator, and now TWO different ones from autozone all have the exact same issue.... I'm wondering if its an alternator problem at all?

Alchemist753 · Fri, Oct-29-2010, 03:20:55 PM

Was pricing alternators just a few days ago for my 2003 M3, the best options I found were:

NEW Valeo from pelican at $341
REMAN Bosch from eeuroparts at $169 + $100 core or bavauto at $170+$73 core

If you are looking locally, NAPA comes in at $245 + $89 core for the REMAN

Bosch part # is AL9407X for my 2003 M3, may differ for late models.

Prices may of course have varied by now. Not sure about shipping costs.

Toxic0n · Fri, Oct-29-2010, 06:04:43 PM

Go to an alternator shop and get the alternator load tested. They should be able to tell you if there is something wrong with it.

k2e15 · Fri, Oct-29-2010, 06:29:21 PM

Cross my fingers, I'm replacing the alternator this afternoon, I hope that this solves the issue and the battery is pretty much brand new!

Itsablurr · Fri, Oct-29-2010, 06:33:37 PM

Quote:

Originally Posted by MY02M3DINAN

Well, considering my factory alternator, and now TWO different ones from autozone all have the exact same issue.... I'm wondering if its an alternator problem at all?

Exactly.

Where is the Voltage Regulator located on your car? That would be the next place to look.

MY02M3DINAN · Fri, Oct-29-2010, 09:31:02 PM

Quote:

Originally Posted by Itsablurr

Exactly.

Where is the Voltage Regulator located on your car? That would be the next place to look.

The Voltage regulator is suppose to be located inside the alternator.

Anyone know if there is a relay or something else involved?

I checked the system again today, when the light is on, the alternator is not charging. I was lucky? enough that it came on and stayed on at start up.

bmw loe · Fri, Oct-29-2010, 10:52:11 PM

buy from www.alternatorpros.com

rebuilt units from Duralast (autozone) have issue's with the voltage regulators not being able to reliably spin to that high of an RPM. I had the same issue with Duralast brand, it's the alternator you put in there, nothing else.

Fri, Oct-29-2010, 03:07:44 AM	#11
deilenberger Moderator Join Date: Dec 2004 Posts: 13,310 Reputation: 578	After checking the connection - you may as well go get a rebuilt one from BMW... what you're seeing is brush bouncing - the slip rings are probably out of round and/or the brushes are worn out and the springs aren't pushing them against the slip rings hard enough. The "rebuilt" ones from Autozone would be better called "repainted" ones.. and since worn brushes are probably the biggest cause of failure, it's not a surprise that the ones you're getting are having problems. If you're real ambitious - take one to a local auto-electrical shop that does alternator rebuilds. They'll have a new regulator/brush assembly that just screws right in, and chances are good that will fix the problem. __________________ Don Eilenberger AKA bellymeisterburgermeister and denilegiiiiiiiiiiiiibennnnegerieragher (but that's misspelled..) 2001 M-Coupe - TiSilver/Black - Das Boot.. 2002 M3C/6 - Imola Red/Black - SOLD 2003 525iT - Green/Tan - SOLD - replaced with Lexus 2006 Cayenne/S - Iceland Silver Metallic/Stone-steel Gray - Truckster. 2007 R1200R - Roadster, black mit/white pinstripes - the REAL BMW.. 2011 Lexus RX-350. SWMBO's new toy.

Fri, Oct-29-2010, 06:29:21 PM	#17
k2e15 Registered User Join Date: Sep 2009 Posts: 355 Reputation: 0 Location: SF/Bay Area	Cross my fingers, I'm replacing the alternator this afternoon, I hope that this solves the issue and the battery is pretty much brand new! __________________ 06' M Lovin every second of it! 2006 Silver Grey M3 Coupe

Fri, Oct-29-2010, 10:52:11 PM	#20
bmw loe Registered User Join Date: Apr 2008 Age: 29 Posts: 922 Reputation: 0 Location: Sarasota/Lakewood Ranch	buy from www.alternatorpros.com rebuilt units from Duralast (autozone) have issue's with the voltage regulators not being able to reliably spin to that high of an RPM. I had the same issue with Duralast brand, it's the alternator you put in there, nothing else. __________________ -e92 335i 6MT Space Gray/Black M-sport, JB4 G5 ISO/DCI/CM Meth (CM10 nozzle) 12.612@114.74mph, 18psi on stock run-flat tires and plausible fuel pump codes sold -e46 M3 6MT, sold -e46 M3 SMG, sold -E90 LCI M3 Interlagos Blue / Novillo Silver

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Fri, Oct-29-2010, 03:20:55 PM	#15
Alchemist753 2003.07 E46 M3 Join Date: Oct 2004 Posts: 189 Reputation: 0 Location: SC	Was pricing alternators just a few days ago for my 2003 M3, the best options I found were: NEW Valeo from pelican at $341 REMAN Bosch from eeuroparts at $169 + $100 core or bavauto at $170+$73 core If you are looking locally, NAPA comes in at $245 + $89 core for the REMAN Bosch part # is AL9407X for my 2003 M3, may differ for late models. Prices may of course have varied by now. Not sure about shipping costs.

Fri, Oct-29-2010, 06:04:43 PM	#16
Toxic0n Registered User Join Date: Aug 2010 Posts: 69 Reputation: 0 Location: Vancouver	Go to an alternator shop and get the alternator load tested. They should be able to tell you if there is something wrong with it.