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Old 04-02-2006, 03:25 PM   #1
ASD123187
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What are the signs of a failing alternator? HELP

Having a very strange and scary problem-

Last night while driving the car, I slowed it down to about 25 on a residential street and the headlights started to flicker (for about 6 seconds), the radio turned off and then back on, and the DSC (!) light flashed off, then back on. (I originally had the DSC turned off.)

Just one minute later at a stop sign the same thing happened, but this time the AC started to flicker, and the ABS light flashed on then off for a second. Then the car stalled!

I started it up, rolled it down the street to my garage and parked it. After I parked it, I had this feeling in my gut and a lump in my throat b/c I almost wanted to cry. I tried restarting the car and it hesitated for a couple seconds, then turned over.

Any idea what the problem could be? I am leaning towards the alternator but am not 100% sure b/c in other threads people seem to refer to bad grounds, dead batteries, and bad sensors.

Any help would be appreciated, so that I could drive my car again. (PS- Not looking forward to being rear ended by a semi on the freeway.)
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Old 04-02-2006, 06:26 PM   #2
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HELP! C'mon, I know somebody around here has had a problem with their alternator!

<~At least steer me in the right direction~>
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Old 04-02-2006, 06:35 PM   #3
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Quote:
Originally Posted by ASD123187
I tried restarting the car and it hesitated for a couple seconds, then turned over.
Went through this a week ago. Just take it to a shop if you're not sure and have them check it out. Mine was replaced under warranty @ the dealer Eventually your car won't turn at all when starting it and u run the risk of it turning off during driving.
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Old 04-02-2006, 08:06 PM   #4
Erick Sermon
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some ppl can tell by listening to the alternator with the car running - it would sound strained. don't know if this applies to BMW.
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Old 04-02-2006, 09:23 PM   #5
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My bet is you need a new battery.
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Old 04-03-2006, 12:06 AM   #6
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Quote:
Originally Posted by hummer
My bet is you need a new battery.
That's the thing, my battery is just a few months old.
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Old 04-03-2006, 03:19 AM   #7
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Had this problem a few months ago, alternator died. Autozone should be able to diagnose your charging system.
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Old 04-03-2006, 04:03 AM   #8
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Plug a Voltmeter to the battery. Battery voltage should be around 12.5/12.7V (if in good health). Turn on the engine. Battery voltage should go up to 13.7V/14V. If not : alternator is dead.

Last edited by Touring325; 04-03-2006 at 04:05 AM.
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Old 04-03-2006, 06:36 AM   #9
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I don't know what's wrong with your car, and I don't know if my experience is typical, but when my alternator died very recently, I had no such symptoms. Car was fine, cruising at 70mph, then the alternator light came on. Checked using voltmeter as above, and confirmed that the alternator was completely dead.
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Old 04-03-2006, 10:00 AM   #10
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Simple-->> get a shop to LOAD test battery..and check alt output
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Old 04-03-2006, 11:50 AM   #11
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Had an alternator die on me in my old '92 MB 190e. Same symptoms.
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Old 04-03-2006, 12:26 PM   #12
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I'll take it to Autozone and have them check the alternator for me. Looks like I'll be getting a new one. So, where did you guys purchase yours and how much did it cost? Did you do a DIY?
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Old 04-03-2006, 01:53 PM   #13
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I was denied warranty coverage for my alternator because of "aftermarket electronics." I purchased a remanufactured Bosch 120 amp unit from bimmerparts.com for $270 (plus $70 core refund). They are close to me, so the cheapest shipping (camel-drawn rickshaw) arrived next day. You can probably find cheaper, if you look around.

I "DIY'd" it. Took about two hours, not including clean-up. There's a semi-useful walkthrough here if you search for "alternator DIY." My input #1: even though both bolts were off the alternator, it wouldn't come out. I yanked and twisted and wiggled and eventually shaved off enough metal that it came loose. It's just those two bolts. My input #2: if you buy the reman unit like I did, take the cover off the cooling tube on the new unit before you put it in the car. My input #3: eyeball the orientation of the top pulley before you take it off - it's slightly offset.

My input #4: having Autozone help you diagnose the problem for free while buying your part elsewhere is just low. If they help you, at least let them sell you a part.
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Old 04-03-2006, 05:02 PM   #14
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can't you just replace the internal regulator inside? Do you have to buy a whole complete alternator? the bentley says you can replace the regulator but then never shows how or talks about it again. the ETK shows it but my parts guy at BMW said he doesn't think he can get alternator parts anymore. i had this same alternator thread the day before ADA posted his, but looks like this one is the only one getting viewed now.
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Old 04-03-2006, 07:12 PM   #15
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Quote:
Originally Posted by ASD123187
I'll take it to Autozone and have them check the alternator for me. Looks like I'll be getting a new one. So, where did you guys purchase yours and how much did it cost? Did you do a DIY?
Had my wife take it to an indy shop, I'm a little preoccupied right now. As far as taking it to Autozone w/o buying the part there, that's where I bought the battery first, so no ethical worries!
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Old 04-03-2006, 07:27 PM   #16
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OK, I had a different problem. Look at my post "Help SES Light On".
http://forum.e46fanatics.com/showthread.php?t=352907
Overcharging from the regulator. Went to several places, Autozone $197+core for Alt, Kragen $201 no core for Alt, Indy parts shop $101 for just the regulator, and now my parts guy OEM BMW regulator $79. So I will be getting a new regulator and see how that goes with install this weekend on my Bosch 120V. Kragen did a diagnostics and found my alternator was putting out too much.
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Old 01-05-2007, 10:00 AM   #17
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How can one DIY test the alternator? Would a voltmeter be suffice for a test?
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Old 01-05-2007, 11:52 AM   #18
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It always helps if you give us all the info to start with. As said above, if the alternator is over charging, the battery will suffer. This makes sence because you didn't get the usual warning light which indicates under charging.
The warning light indicates low alternator output and tells you that the power is coming from the battery. Alternator output should be 14+ volts. I would agree that a new regulator should fix this. I also bet there are a lot of perfectly good alternators changed when the real problem is the regulator!
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Old 01-05-2007, 12:04 PM   #19
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Alternator test

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Originally Posted by vids_blk323Ci View Post
How can one DIY test the alternator? Would a voltmeter be suffice for a test?
From my past experience. As mentioned above, using the voltmeter check the battery terminal before and after you have turned the car on. Before turning the car on, it should read 12.4V and after the car is on, it should read above 14V.

The second way of testing (Be carefull) is to take off the negative cable off the battery while the car is running. If the car keeps running, that means that the alternator is supplying enough juice to keep it running. If the car dies, then it was using the battery alone and you need to change the alternator.

Good luck
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Old 01-05-2007, 03:47 PM   #20
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From my past experience. As mentioned above, using the voltmeter check the battery terminal before and after you have turned the car on. Before turning the car on, it should read 12.4V and after the car is on, it should read above 14V.

The second way of testing (Be carefull) is to take off the negative cable off the battery while the car is running. If the car keeps running, that means that the alternator is supplying enough juice to keep it running. If the car dies, then it was using the battery alone and you need to change the alternator.

Good luck
DO NOT remove that negative battery cable while the car is running. You WILL get a voltage spike and there's a good chance it will take out some electrical components. That "trick" is safe on older cars with point ignition.

As noted earlier, a voltmeter can be used to verify that the alternator is putting out power and that the regulator is working. Max voltage should be under 15v, even if the engine RPMs are increased. Voltage should stay above 12.5v even at idle with full electrical load (lights and A/C on). Output is measured in AMPS and typically requires a meter designed to test charging systems (you could also wire up a standard amp meter with an appropriate shunt, but you have to do that in series). Many on-vehicle alternator testing rigs use an inductive clamp to measure current flow.
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