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Noob
Join Date: Apr 2013
Location: Murfreesboro, TN
Posts: 2
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Voltage Problem
Hi All,
New to me early 1977 320i. Prior Owner put in new alternator. I put in a new battery. Have only driven the car a few days. Battery (engine off) meters at 11.88V this morning Battery (engine on) meters at 7.8V this evening Battery (engine off) meters at 8.8V this evening Alternator bad? What should I do next? Thanks |
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04-19-2013, 05:08 PM
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Registered
Join Date: Sep 2005
Location: Sacramento CA
Posts: 1,147
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Alternator is not charging. The question is, why? Bad connection at alternator? Bad ground at alternator? Bad connection between alternator and battery? Failed Alternator? Failed voltage regulator? The voltage regulator attaches to the back of the alternator with two screws. Costs about $15. The brushes on the voltage regulator wear out every 125-150k miles.
Is the alternator a name brand factory rebuild or whatever rebuilt they had at the local auto parts store? If the battery is fully charged, you should see 12.6 Volts DC with the car turned off and 13.5-14 Volts DC with the car running. Do you know whether this alternator has ever charged since the PO put it on? How long ago was that? |
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04-19-2013, 07:05 PM
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Noob
Join Date: Apr 2013
Location: Murfreesboro, TN
Posts: 2
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Alternator
Manolito
Thanks for the reply. I'm a former Californian myself (Visalia), now in TN. I got the car 1 month ago. The PO did the alternator maybe 2 months ago. The alternator is re-manufactured, believe it to be an off-brand. I cannot verify that it ever charged. They had it on a battery charger when I picked it up. The VR looks new, and I have a spare old one. Is there any point in swapping, or do you think this rebuild ALT is just crap? Billy |
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04-19-2013, 07:25 PM
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Registered
Join Date: Sep 2005
Location: Sacramento CA
Posts: 1,147
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A lot of rebuilt alternators and starters come from small rebuilders in Mexico and their quality control is less than 100%.
That being said, it is more likely that the car has a wiring/ground problem and the alternator itself was not the problem in the first place. At this point, I would get a good wiring diagram (is there a Bentley manual for your model?) and a voltmeter and start methodically going through the charging system wiring. Swapping the voltage regulator is a low probability experiment, but not hard to do. |
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04-20-2013, 08:03 AM
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