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E85 / E86 Z4 (2003-2008)
E85 Z4 Roadster, E86 Z4 Coupe, E85 Z4 M Roadster, and E86 Z4 M Coupe talk with our BMW gurus here.

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  #1  
Old 08-16-2013, 09:22 AM
lpcapital lpcapital is offline
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Mein Auto: Wasp & Duc
My story about voltage regulator

After 10 years and 120K miles something in the Z4 finally decided to go bad!!!! I was on my way home and the battery light came on; after quickly pulling over to ensure the serpentine belt was fine, I figured it was the voltage regulator. As a matter of fact, once I got home and checked the voltage with a volt meter I noticed it was in the lo 11v and occasionally dropping down to 6v.

In the Z4 you have so much room that removing the voltage regulator requires only to remove the airbox, and then you have access to it real quick. As I expected after removal, the brushes was somewhat low and I suspect that were not providing a good contact on the rotor causing erratic voltage.

You see, alternator are briliantly simple and there's generally no reason to replace the whole thing. Other than the brushes, the other thing that could happen is that the bearings on the rotor go and they get noisy. The diode bridge of the rectifier rarely brakes (unless you have other electrical problems in the car, or you invert polarity...) and if they do, you normally get over voltage situation or AC in the circuit and I'm sure thaere are many failsafes... But enough talking about what doesn't go bad.

Anyway, I thought I would share a couple of pictures, just cuz...

Old on the left, new on the right



Old



New



The harder part was actually dealing with the mess in part numbers. In the case of the Z4 I was lucky that BMW lists the voltage regulator as a spare part on real OEM, but when I had similar problems on the X3, RealOEM actually listed 2 alternator (a Valeo and a Bosch) and no replacement part for the voltage regulator.

My suggestion to you: remove the old regulator and plug in the part number of the manufacturer (not BMW) into Google and let Mountain View do the work...

At the end, I found the regulator on Amazon for 60 bucks; it came in quickly and once installed, voltage is back at 14v steady at idle...

Life is good and now I guess I can go back 10 years and another 120K miles before seeing another warning light...
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2003 BMW Z4 2.5i
2009 BMW X5 xDrive35d
2006 Ducati 999S
1999 Ducati Monster 750

Last edited by lpcapital; 08-16-2013 at 10:24 AM.
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  #2  
Old 08-16-2013, 11:10 AM
kalali kalali is offline
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Mein Auto: 2003 Z4 2.5
Thanks for sharing. Is that piece bolted behind the alternator or is a separate unit? And could you please post the part number you ordered? My Z4 is about as old as yours so I'd like to be prepared..
Thanks.
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  #3  
Old 08-16-2013, 12:09 PM
lpcapital lpcapital is offline
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Mein Auto: Wasp & Duc
Quote:
Originally Posted by kalali View Post
Thanks for sharing. Is that piece bolted behind the alternator or is a separate unit? And could you please post the part number you ordered? My Z4 is about as old as yours so I'd like to be prepared..
Thanks.
The voltage regulator on pretty much all internally regulated alternators is mounted on the back of the alternator. Here's how it looks:



There is a plastic cover (where the white BMW sticker is) held in place by two nuts (one behind the positive wire and one on the negative which is behind a cap - the alternator is grounded through the engine case) and a Philips bolt. You cana ctually see part of the voltage regulator on the top where it says BR14-CO.

Now, if you look at the while label, you'll see at the bottom, right above the BMW logo a part number 0124 515 105: that is the Bosch p/n for the alternator.

On this website I was able to get the Bosch part breakdown: http://www.wo***********/Unit.aspx?M...Ref=0124515105

There you'll see the part number for the voltage regulator and if you click on it you'll get here: http://www.wo***********/Component.aspx?Ref=VRG46478

On that last page you'll see a cross reference of all the Bosch voltage regulator that are compatible; namely:
F00M145280 (the code inprinted on the one I removed)
F00M145679
F00MA45219 (the code inprinted on the one I bought)

The you go on Amazon and using their care selector tool it proposes you a Bosch voltage regulator that has a part number: W0133-1665703... That's where Google helps to match up the two and ensuring you're getting the right now. I preferred buy it Amazon because in case it came in ant it wasn't the right one, it was painless to return and start all over.
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2003 BMW Z4 2.5i
2009 BMW X5 xDrive35d
2006 Ducati 999S
1999 Ducati Monster 750
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  #4  
Old 08-17-2013, 06:32 AM
kalali kalali is offline
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Mein Auto: 2003 Z4 2.5
Thank you so very much for taking the time to explain all the details. Much appreciate it.
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  #5  
Old 08-19-2013, 11:41 PM
Lunas72 Lunas72 is offline
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Location: Seoul, South Korea
 
Join Date: Jul 2012
Posts: 2
Mein Auto: 2003 2.5i Z4
BSD Cable

By any chance do you have the part number for the BSD cable?

Thanks.
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  #6  
Old 03-14-2014, 03:57 AM
Divepatches Divepatches is offline
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Join Date: Nov 2008
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Mein Auto: BMW Z4
I bought a rebuilt Bosch alternator from Autozone (Duralast). It would only charge for about 20 minutes. Autozone said it must be a loose connection or the DME (ICU). After a lor of research I found that the regulator was bad. I replaced it with a NAPA Bosch OEM regulator and the problem was solved. It cost $145. In my opinion this should have been good in a rebuilt alternator but Duarlast does not check to this detail. they just replace the brushes and do a bench test which it would have passed.

If I had it to do over again I would have bought a NAPA Bosch OEM alternator and saved time and money. Duralast alternator was about $200.00 and the regulator was about $145.00 making the entire replacement $345.00 and a lot of extra work. A new Bosch alternator is $299.00 at NAPA.

There was a lot of misinformation posted on the E86 alternator and charging system. There is no IBS on the E86 so don't try to troubleshoot this. The DME does control charging but a quick test recommended by Bosch tech support narrowed down the problem to the regulator.

Bosch tech support told me that if the control from the DME and plugs in to the regulator on the alternator is removed the default is to charge continuously. I removed the plug and the alternator did the same thing it had been doing. It charged for 20 minutes then cutout. It then flipped back and forth from charging for 15 seconds to not charging for about 2 minutes. After I replaced the regulator it charged properly and the battery light is out. Everything is good now.
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  #7  
Old 03-14-2014, 08:11 PM
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dc_wright dc_wright is offline
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Mein Auto: '96 328iC, '04 325Ci
I had an E36 before my Z4 and you wouldn't believe how many "bad" rebuilt alternators people reported in that forum that they got from AutoZone for their cars. In some cases multiple times before going to NAPA or a pick a part lot and getting one that worked.
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