Technical Starting Problems

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Technical Starting Problems

DELDAN

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Joined
Jun 17, 2013
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Surrey
Thoughts please, 2003 Mk II 2.0 JTD has started to have flat battery symptoms, with occasional 'not charging' messages ending up with a total failure to turn over and the breakdown guy saying that he was surprised the battery would not turn it over but the jump start fixed it anyway! Got home and checked the battery which was only showing about 12v and when measured with the engine running about 12.4v at idle and 12.8v at 1500. Concluded the alternator was faulty so I changed it for a new one which has been fine for about a month then yesterday no turnover again, measured the battery voltage at 11.8v. Now digging harder, I checked the alternator earthing it out to the block and it is giving a minimum of 13.8v, I think it is the same cable running straight through the under bonnet drivers side wing fuse box and I still have 13.8v but at the battery a good deal less only around 12.4v, Questions a) Is it the same cable connecting the alternator to the Battery that runs through the fuse box? b) Is there anything between the fuse box and the battery (it is very difficult to see) to drag the volts down? c) Could the battery be faulty and affecting the measurement at the terminal? d) There seems to be a very elaborate connection at the clip on terminal on the battery positive terminal - is it special in some way? Any ideas would be appreciated.
 
The thick lead goes from the alternator to the fuse box in the engine bay, it piggy backs on to a similar lead which then goes through the bulkhead down under the carpet to the + battery terminal.
 
Thanks Fran. I found a pic that suggests the through bulkhead cable is just a straight run with nothing inline to cause problems. So trying to think logically - 13.8v measured Alternator to Block but 1v less measured Battery to Body. I tried running a new earth lead (I could not find the original) between the body and the block and hey presto a much better charging reading and so far no more problems.
 
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