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      08-27-2025, 03:12 PM   #59
Edwardsc1
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Drives: 2011 BMW M3 Comp
Join Date: Nov 2019
Location: Greenville, SC

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2019 X5  [0.00]
2011 BMW E92 M3  [0.00]
Quote:
Originally Posted by Redd View Post
Now, assuming your ground strap is ok and your new alt is original BMW (I've seen weird behavior with new OEM alts) the weird voltage reading you're seeing might be normal. As long as your car starts and doesn't throw any errors, it could be normal behavior after a new batt registration. Monitor it for a few weeks - around 1000 kms - and see if it sorts itself out.
Appreciate the reply. I should be able to check my ground strap this weekend.

I've been able to replicate the problem every time now. The voltage only drops below 13.5V when I turn the car off for a short period and then turn it back on (getting gas, going to the store). It will then sit around 12V and slowly drop down during the duration of my drive. Usually down around 11.4-11.5V after a 30 minute drive. If the car sits for a few hours, or overnight, then it's perfectly fine. Running between 13.5 - 14.3V.

I did get a Bosch/ Valeo unit from FCP Euro, it was not directly from BMW or a BMW branded alternator.

Edit: I did not re-register my battery after replacing the alternator. Just replaced the alternator and plugged the battery back up.
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