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Discussion Starter #1
I have posted about this on another site too, because I need to make my decision quickly. I am about ready to change out the alternator on my daughter's 2006 wagon with a rebuilt unit I have on the shelf.

BUT I am not sure I have ruled out other causes. The symptom is that voltage surges between 14V and 15.3V or so for a minute or two or three when the car is first started from "cold" (70 to 80 degrees F). The halogen headlights noticeably change brightness - but then the voltage settles back to the normal 14.3V or so, and stays fairly constant. The resting battery voltage is an acceptable 12.37V. Recent testing of the battery cables seems to rule them out - and what I am seeing is to much power, not a power loss.

WIS shows the charging system electrical diagram without any control from the ECM to override the alternator's internal regulation of output. With well over 100K miles on the alternator and its regulator, I think the regulator is the likely culprit. Does anyone know for certain whether there is any external control of output from these alternators ?

Thanks for input !
 

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external control was available for 9-5 II, but not for 2006.
Replace the regulator (or complete alternator), most probably it is broken.
Is replacement alternator also 140A version? I think connector position and therefore cable length are different, maybe older 130A will not fit.
It should be possible to just replace the regulator with the alternator dismounted from the bracket, but still in the car. Therefore you dont have to pull it out completly.
 

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It’s just the regulator that’s bad. It is in/on the back of the alternator. Taking the alternator out is a horrible job. There are videos on YouTube. If you can replace just the regular without having to completely remove the alternator, it’s a bit easier
 

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Discussion Starter #4
Thanks for info - locally rebuilt alternator (new bearings and regulator/brush assembly) will go in this afternoon.
 

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Discussion Starter #5
New alternator fixed the issue.

Headlights are now steady from start, voltage (at battery) is solid 13.98 to 14.00 Volts. I had never experienced an alternator that went bad by producing too high a voltage. It's a shame I did not think to turn my VOM to AC Voltage to look for ripple . . . . I suspect bad regulator, so I will have that unit professionally & locally rebuilt to be sure to have new bearings and regulator / brush assembly.
 

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I had a Kahler voltage regulator go out in my 9-5. It put out voltage spikes and did some very strange things. It blew the headlight bulbs, produced static in the radio, and messed with the transmission computer. It did that twice before I realized what was going on. The same brand voltage regulator also failed in my 1997 900. In that car, I noticed it because the wipers were running way too fast.
 
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