12-04-2012, 08:20 PM
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Cruising 280 Top Down
Location: San Jose, CA
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Join Date: Jul 2010
Posts: 4,998
Mein Auto: '99 M3 Cab & '05 X5 4.8is
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Quote:
Originally Posted by pablo645
+1. I would have the alternator checked. You could do it if you have a multimeter as well. If you connect the leads to the ground (Car frame) and to the +Pos terminal before starting the car, you should be reading battery volatge of 12V DC. Then start the car and you should see the voltage go up to approximately 14V DC. this should remain a constant value. If the volatge is irratic, then the alternator regulator might be bad. (I'm going by memory here so bare with me  ) |
Exactly. as low as 13.5 is probably OK, but you want to see 13.7 to 15V to charge the battery properly. Any variation that isn't accounted for (slight dips when you turn on the lights, slight jumps when you rev the car, etc.) is a faulty regulator, or alternator, or both. When you get a new alternator, it should come with a new regulator. Unless you are 100% certain it is not the regulator, replace it too! 
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Quote:
Originally Posted by EnserioJose
Sorry. I'd imagine Seattle is a-hella-nother country.
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2005 X5 4.8is Le Mans/Black/6spd Steptragic 
1999 M3 Cabrio TiAg Metallic/Dove Grey/Black 5 Speed Manual
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1997 328iC Schwarz II/K/K 5 Speed Manual SOLD 5/2012
2004 645Ci Mineral Silver Metallic/Black 6 Speed Manual RIP 04/2011
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