Originally Posted by RenaissanceMan

After I posted I went ahead and picked up an alternator and swapped it out. Problem appears to have disappeared for now. Maybe I was premature in not just changing out the voltage regulator, but I figured I'd go ahead and knock the alternator out since I got a pretty good discount on it.

BigBody, the reason the voltage went down to nine is because the X5 was only running off of the battery, which was not being charged by the alternator. If you are taking a reading off of the battery from a car that is running properly, you should not have only 12 volts. It should be closer to 14, because you're getting regenerative power off the alternator. When mine stopped charging, the voltage I was reading off of the battery was the same as if I had the battery out of the car, so the longer I drove the more the battery was depleted. That's what took me so far down to 9 volts in the first place. My alternator had momentarily stopped working for about 20 miles worth of driving.

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