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Discussion Starter · #1 · (Edited)
FIXED AFTER CHANGING TO THE 4TH ALTERNATOR


Hello, I've been reading post for days now and can't figure out what's going on with my car. It's a 04 530i with something like 120 thousand miles. The other week on the way to work I got a charging malfunction warning flash across the screen then again a couple miles later but not check engine light. After getting to work 20min later I went in the secret menu and it was charging at 11.9v. Drove home the next morning and no warning lights or anything but still only charging at 11.9v. Changed the alternator with a Bosch and when it started up it read 14.3v then at it warmed out it dropped to 11.9v. So I changed the alternator again and it did exactly the same thing. Does anyone have any ideas what could be going on
 

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Or something wrong on BSD bus which also controls the alternator. Check trouble codes with diagnostics. If you leave the small plug on alternator disconnected it should work without BSD in a fail safe mode on constant voltage about 14 V.
 

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Discussion Starter · #5 ·
Or something wrong on BSD bus which also controls the alternator. Check trouble codes with diagnostics. If you leave the small plug on alternator disconnected it should work without BSD in a fail safe mode on constant voltage about 14 V.
I left the small plug unplugged and it says 12.9v at start up as soon as I plugged it back in it jumped up to 13.9v and as soon as I turned the lights on it dropped to 12.7v then after warm up it drops to 11.9v no matter lights on or not
 

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I left the small plug unplugged and it says 12.9v at start up as soon as I plugged it back in it jumped up to 13.9v and as soon as I turned the lights on it dropped to 12.7v then after warm up it drops to 11.9v no matter lights on or not
What if you throttle it higher revs?
 

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Discussion Starter · #8 ·
Now today I drive it up to get my kids off the bus witch is only 1/2 mile or so. Well sitting up there for the charging malfunction 3 different times and was charging over 13 volts each time after 10min or so it dropped to the 11.9 for a while like it had been fluctuating around a bit and then shot up to 15.5 and stayed at 15 to 15.5v until I drove back let it idle for a bit and shut it off. This damn car makes no since to me at all
 
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