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battery drain, 300tdi


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#1 Jiminy Cricket

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Posted 04 March 2012 - 10:27 AM

Before I start I have tried to read all posts on here and in the tech archive.....but I'm still stumped. Help please! Ok so battery went dead (on wife when I was at work......truck is running out of lives!). Have fully charged and tested battery, its good. Vehicle now starts well everytime, but we have to disconnect the neg terminal. Tried testing in line with neg lead using a lamp (spare reversing one) with all turned off. Lamp glowe very bright, so I thought brilliant this won't take long.......silly man! I have pulled every fuse (i think) to try and get the light to dim, but nothing.....are there any others hidden in a 300tdi defender other than main fuse box and engine bay next to the heather matrix? Also is the lamp test I am doing going to work.....I think it should, obviously an ameter would be better but the fuses in my multimeter seem to hve blown, great!
Any pointers / advice appreciated......the wifes getting board of connecting / disconnecting the battery 10 times a day! Oh, and it drained the battery in under 12 hours to nearly usless, so must be something big ish???

#2 western

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Posted 04 March 2012 - 10:55 AM

Have you had the alternator tested, could be a internal fault draining the battery.
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#3 Jiminy Cricket

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Posted 04 March 2012 - 11:09 AM

Not yet, will do though....thanks for the advice!

#4 danebrewer

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Posted 04 March 2012 - 11:12 AM

is it possibly a wire with some worn insulation somewhere, could be shorting out in some metalwork?

#5 Eightpot

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Posted 04 March 2012 - 11:36 AM

it doesn't have to be a big problem to drain the battery like that. I had the same problem recently and it was a very thin gauge wire that ironically connected my battery monitoring gauge - had just been rubbing a little on a bracket and was earthing out. Drained two big numax batteries in four hours.

I normally use a digital multimeter switched to the continuity setting , and the earth probe grounded, touch the other probe onto the various circuits. If you get a positive reading on a circuit you can start narrowing it down fairly quickly. You'll need a circuit diagram and be able to read it to get very far though, the haynes diagrams are generally ok.

#6 scube

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Posted 04 March 2012 - 11:38 AM

I agree with Recovery Man

I had a similar problem when by accident I caused a short on the battery and it fried one of the diodes in alternator and allowed the alternator to bleed charge from the battery when the engine was not running, at first it would take a couple of days to drain but in a very short time I was having trouble every morning, I ended up doing what your doing and disconnect the battery when ever I left it for a while.

I found the problem by putting a meter in line with the battery measuring the current drawn and disconnecting things until I found what was causing the problem.
Removing the small wires from the back of the alternator was all it needed to stop the charge drain.
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#7 cackshifter

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Posted 04 March 2012 - 01:16 PM

Try leaving your bulb in the negative for a moment, and removing the 4 maxi fuses under the bonnet near the heater on the LHS in turn. If that doesn't put the light out it doesn't leave much - alternator and starter basically, though there is a'diagnostic socket' fed via a fuse; I think this is in the battery box though I may be wrong, and if that is shorting it may cause the problem .If the light's still on disconnect alternator next, easier than starter, then you're looking at the starter. If OTOH one of the fuses extinguishes the light, its in one of the circuits fed from it, but it narrows it down a bit - you then have to repeat the process with the main fuse box. Do you have the wiring diagram btw.?

#8 Jiminy Cricket

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Posted 04 March 2012 - 07:36 PM

Guys, thanks for all the advice......finally got round to looking at her.......and diagnosis is alternator. When I disconnect the main charging lead my test lamp all but goes out. I assume that means a new alternator....or a recon.....any tips on where to go if so.....and what to avoid! Thanks again.




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