Moonie
Member Since: 28 Feb 2010
Location: Whitby North Yorkshire
Posts: 178
 
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Evening all, my battery light came on yesterday on the to Driffield, managed to get there and back without any probs. Just checked the on board diagnostics and its sitting at 13v with no change. Could this just be a faulty sensor. 
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 22nd Aug 2010 5:55 pm |
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J@mes
Member Since: 10 Nov 2008
Location: Bomber County
Posts: 4547
  
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Put every electrical item on in the car and drive for 10 miles.....it will drop to 9v before the screen goes off and then you know your alternator has gone - just make sure you have recovery....  2014 D4 XS
2005 D3 SE - Gone
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| 22nd Aug 2010 6:14 pm |
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Robbie
Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932
 
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I don't like the onboard diagnostics as mine seems a good volt out and only seems to report every 0.5v. I put more faith in a real multimeter.
Suggest you test the real voltage before and after having the lights on for 5~10 min. With a good battery there should be almost no difference. After that you are looking for a good output on the alternator.
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| 22nd Aug 2010 6:15 pm |
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Moonie
Member Since: 28 Feb 2010
Location: Whitby North Yorkshire
Posts: 178
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I`ve done about 100 miles since it came on I didnt think the battery would last that long if it`s the alternator.
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| 22nd Aug 2010 6:19 pm |
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Robbie
Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932
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With worn brushes an alternator can give some output for quite a while; although a sudden death with bad brushes is not uncommon either. A multimeter should reveal all.
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| 22nd Aug 2010 6:23 pm |
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Tawny Owl
Member Since: 22 Oct 2008
Location: Here and there
Posts: 1645
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@ 13volts the alternator will be putting a small amount in and as long as heavy loads aren't being used this is probably why you managed 100 miles.
Get a amp clamp around the battery cables and check what amperage your getting and also a multimeter.
Should be up around 14.5 volts charging 
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| 22nd Aug 2010 8:25 pm |
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