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Hi to all I have a problem I wonder if anyone can help.My defender 90 battery is draining overnight,so I thought I would turn everything off, and remove the neg lead.I put a multimeter from neg terminal to neg lead and check fuses.But unfortunately the reading I am getting on the meter is 12.7v the same if i touch the body.

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Hello, the voltage drop will be minimal. What you need to do is put the meter on Amps (or milli-amps), remove the battery positive lead and then put the meter between the battery positive and the battery positive lead (that is in series completing the circuit). That will tell you the current drain.

Then remove each fuse one by one and see what circuit is causing the drain.

Cheers

Peter

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Thank you Peter for your quick reply.I will check this out today? Trevor

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Hi not a good day today.Did a test multimeter went out of range,so moved up to a 10amp test with everthing off the draw was 3.2 amps, checked all fuses no change been checking other fuses winch ect as yet no luck? Trevor

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3.2Amps @12V means something like 40 Watts of power is going somewhere!

That will be making something somewhere rather warm.

Try feeling the alternator-casing some hours after the engine's been run to see if it's still noticeably hot - in the past I've seen failed diodes/regulators continue to energise the alternator rotor when the engine's stopped.

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Posted (edited)

 Circuits that are switch controlled are dead so no need to test them, but an iffy alternator with a faulty diode/ regulator will drain a battery overnight, diodes can be tested but the time it takes it’s just as easy fit a new pack.

Edited by teabag
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Thanks you Guys for the info, I will do some more checks today especially the alternator Trevor

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Thanks all  Progress at last, removed all alternator leads had another battery check drain just a few milliamps so the problem is there somewhere.

but at the moment rain has stopped play. Trevor

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As others said, with a result like that it'll be something in the regulator pack, likely a diode or two. A lot of alternators you can replace the reg pack quite easily, often in-situ.

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2 hours ago, FridgeFreezer said:

As others said, with a result like that it'll be something in the regulator pack, likely a diode or two. A lot of alternators you can replace the reg pack quite easily, often in-situ.

Any idea how easy it is to do the bearings on an alternator?

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not easy at all, without a bearing press, much quicker to buy/fit a new or recon alternator & could be used as an excuse to upgrade the rated output i'e' - 65amp for a 100 or 120amp plus increase the wiring diameter from alt to starter/battery.

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Thanks, Ralph.  The wiring was done years ago to 100A, but it’s just a 65A alternator and a 100 is the plan.  I was just thinking of keeping the 65 as a spare if I could sort the noisy bearings - it works well and doesn’t have any play, just a bit noisy on the front (I think it’s the bearing rather than the pulley, which looks like new).

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Only person I've known do alternator bearings is Daan, and that alternator then failed in very short order on the way to a ferry :ph34r:

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I have done several in the past but as Ralph mentions you need the right pullers. The cost of new ones complete with pulleys has dropped so much now that it is hardly worth the faff. However still willing to do them for forum members if you can get them to me.

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