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      02-03-2015, 09:54 AM   #1
Zkhan77
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Alternator on its way out?

MCoupe is parked for the winter so I let it run for about 20 mins over the weekends and just sit in it waiting for this Chicago winter to end. Anyway, it didn't fire up on Saturday so I put it on the charger for the night. Battery read out a steady 12.5V before starting. After about 10 minutes with no load, I monitored the battery and it was up and down between 13.8-14 V, after turning the heat on full, lights and heated seats on, it dipped just below 12 then hung around 12.2-12.5V and never recovered to 13-14V. Car has just around 70K miles on it and a 2 year old battery. I've read posts about the alternator failing earlier than my mileage, and not wanting to drive through the salted roads ...Would an indy shop do anything different to test?

Appreciate the help,

Z
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      02-03-2015, 12:27 PM   #2
Karacticus
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If you've got a multimeter that can read true RMS AC voltage (like a nice Fluke), you could check to see if there's any significant AC voltage on the bus. If there is, you've got a least one bad diode in the rectifier/regulator of the alternator.
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      02-03-2015, 04:48 PM   #3
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alternators going on the z4 seem to be a relatively common issue!
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