devildawg712

Interesting, pardon my ignorance, but where is the correlation to the error and time of occurrence? Is it still an issue of power? I guess I can add that to my list of things to do if all else fails. How much was the sensor and can it be a DIY or does it need to be done professionally.

and for what it's worth my error message usually happens to me on the freeway or just driving normally so I'm still not too convinced it's down that road. Good to look into tho. Thanks again.

BimmerFan52

I plugged my voltmeter in today and rechecked my numbers.

Before starting 12.6V. Upon starting voltage immediately jumped to 15V for 2-3 seconds then straight to 14.7V where it held steady. After full warmup while driving it bounced around, never going below 14.3V and never above 14.7V.

My FLA battery was replaced with an AGM battery (replaced and coded by a dealer) in February of 2012, which is why it correctly stays below the maximum 14.8V.

devildawg712

Is it supposed to jump? Mine drops when I start the engine. And it also never goes above 14.1 from my observations. Again tho, it's only been 2 days and mediocre driving.

balbs

I was lucky and my car was under warranty at the time. The SZL was about $500 to replace. However, I saw a thread on M5Board on how to clean it with just compressed air. It seems it just gets dirty. IIRC, it threw an error code according to the work order. I would check for codes on the car.

Would the car throw codes if the alternator is going out? With all the tech on the car I would be surprised if it didn't.

BimmerFan52

Yes. Before starting you are measuring the battery voltage only. You said 12.5-12.6V which is fine.

After starting the car the alternator establishes the system voltage and should immediately start outputting at the very least 14.3V and usually 14.5-14.7V depending upon the battery state of charge. If the battery state of charge is low a FLA can charge up to 15.5V.

11.2V just after starting is way too low, and suggests that your voltage regulator is on the way out.

Get an auto store to confirm that diagnosis for free.

SlvrBmr545

devildawg712 damn every time I see that ride of yours I drool on myself !! LOL Love the color combo,rims,nose,and hood . Slammin

balbs

Curious? How much is a new voltage regulator and is it an easy DIY?

balbs

Based on the values you guys are posting, I think mine is going.

BimmerFan52

Generally voltage regulator is around $50. Link below, but double check the PN as that was the first one I found for a Valeo 180A and may not be the correct one for yours.

After I investigated the time to pull the alternator to get at the voltage regulator (screwed to back side) I decided to put in a brand new OE Valeo alternator (just under $300). In addition to the voltage regulator the brushes, bearings and windings can all fail, and I didn't want to replace just the voltage regulator and then be pulling it apart again a year later because something else failed.

You can buy rebuilt also, but I have heard good and bad about the quality of rebuilt.

BMW Voltage Regulator 12318510090

devildawg712

Ahh.. Thank you thank you. All great info that greatly aids me in inching my way to a final diagnosis. Do I need to remove my entire alternator to get this checked out or can they determine that the voltage regulator is beginning to fail with the OBDII scanner? My Indy initially did like a quick 10 min. scan of both my battery and alternator and said both were fine. (this was like a week and a half ago, which led me to run around in circles trying to find out what the heck could be setting this off). Yea, screw it. Entire new unit will be replaced.

Thanks brotha. I hope this thing will make it to 200k+.