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Old 04-01-2012, 11:45 PM   #16
OVERKILL
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It really sounds like the battery. Take it and get it load tested at a place like CT. I'm betting it fails.
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Old 04-01-2012, 11:55 PM   #17
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If it was the battery the voltmeter would still read a higher voltage when the car is on as the alternator is attempting to charge it because at that point you're readout is the voltage of the alternator and not of the battery.

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Old 04-01-2012, 11:56 PM   #18
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If it was the battery the voltmeter would still read a higher voltage when the car is on as the alternator is attempting to charge it because at that point you're readout is the voltage of the alternator and not of the battery.

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The car ran without the battery however. This means that the alternator IS working. Perfectly? Well, that's another topic. But getting the battery load tested would be my first step.
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Old 04-02-2012, 12:01 AM   #19
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What do you mean it ran without the battery? Once a car is turned on it requires very little additional voltage to actually stay on.

Explain the 11V readout with voltmeter.


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Old 04-02-2012, 12:03 AM   #20
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What do you mean it ran without the battery? Once a car is turned on it requires very little additional voltage to actually stay on.

Explain the 11V readout with voltmeter.


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Also i tried to boost the car, it started then i unplugged the battery, it ran the same till i put a load on (turned on the lights). Then the car instantly turned off.
The car ran on the alternator alone. Not great for the alternator, that's for sure.

And now the other issue is that if the car was running with a dead battery for a while, this is incredibly hard on, and will kill an alternator. So he may end up having to replace both at this point if that is indeed the case.
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Old 04-02-2012, 08:40 AM   #21
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Well im sittin here now running the car after giving it a boost. With nothing on it sits at 12.75. I turn on the lights.... Drops to 9.45. Add the high speez heater fan... DroPs to 5.something, then car shuts off after car shuts off volt meter shows 7.52
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Old 04-02-2012, 08:52 AM   #22
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Well im sittin here now running the car after giving it a boost. With nothing on it sits at 12.75. I turn on the lights.... Drops to 9.45. Add the high speez heater fan... DroPs to 5.something, then car shuts off after car shuts off volt meter shows 7.52
Looks like your alternator or VR is gone. Why not take it to a garage and get them to diagnose it?
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Old 04-02-2012, 08:58 AM   #23
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Looks like your alternator or VR is gone. Why not take it to a garage and get them to diagnose it?
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Old 04-02-2012, 10:42 AM   #24
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Well im sittin here now running the car after giving it a boost. With nothing on it sits at 12.75. I turn on the lights.... Drops to 9.45. Add the high speez heater fan... DroPs to 5.something, then car shuts off after car shuts off volt meter shows 7.52
What are you boosting it with? A booster pack or another vehicle? You could continue to troubleshoot it but you probably need a battery, alternator or both at this point. If the battery failed and you ran the car off the alternator, that will cook the alternator.

A place like CT or NAPA should be able to both load test the battery and test the alternator. The battery is the easiest, since you can just pull it and take it there. However, with the battery drained, it will need to be charged first. Do you have access to a battery charger?
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Old 04-02-2012, 12:32 PM   #25
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I know I can buy the actual voltage regulator but if it's built in or not I'm not exactly sure, it has the same alt. As the 1991 525i m50b25 if that helps

^^ easy thing to do is swap in the good alternator from the other car into the affected car and see if that solves your problem. If it does, then alternator issue, and you have to now decide if the alternator needs to be rebuilt or the VR needs to be swapped with a new one.
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Old 04-02-2012, 04:24 PM   #26
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Alright so i finished up, its all good now, my battery had 2 cells that were feeucked and my alternator got bench tested at Part source and it wouldnt even spin up due to the circuit being finished
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Old 04-02-2012, 04:35 PM   #27
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Alright so i finished up, its all good now, my battery had 2 cells that were feeucked and my alternator got bench tested at Part source and it wouldnt even spin up due to the circuit being finished
Called it lol

This is a pretty typical (and dare I say common) failure model. The battery loses a cell or two and refuses to hold a proper float charge, subsequently over working and killing the alternator.

And it sucks because it is a bit of a double-whammy to the pocketbook as well.

Glad to hear you got it all sorted out.
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Old 04-02-2012, 07:26 PM   #28
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Thanks guys! Good one calling that, im happy to be bck on the road, thanks again*
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