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battery drain when stood

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right so iv been having this problem with my 90. flattened the battery when the alternator failed so i charged the battery fully and changed the alternator.

next morning i went to start the car and there wasnt even enough power to make my LED for the alarm flash. so again i charged the battery and started the car straight away when it was done, i noticed that the battery light didnt come on when i turned the key, it stayed off.

so....next i tested the alternator charge at the battery and it was fine so i discounted that, tried all my lights and they all work even the interior ones.

i wanted to re-do all my winch wiring anyway so all that came out to until all that was left was the positive and negative from the main loom.

put a fully charged battery on the car and next day dead as a dodo and my patience is very thin with it.

only thing i havnt tried is my towing socket thats new but its the original wiring.

anyone who can understand this rant please help.

any help or advice would be massively appreciated

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Hi mate, you really need to do a parasitic drain test, so really youll need a multimeter capable of measuring upto say 10A (not mA). You then need to disconnect the negative lead and connect the meter in series between the lead and the battery post.

This will then give you a reading of how much current is being drawn whilst the car is off. (make sure and door contact switches etc are taped up so it thinks the doors shut).

Its pretty much a case then of going through all the wiring, disconnecting fuses or wires untill the current drawn drops down to a few mA.

They say at rest a car should pull no more than say 50mA, although my Audi pulls 200mA and thats apparently normal for it, either way, I would say no more than 50mA on a Defender, depending on any alarms etc you have installed.

The other thing to note is that if the battery is goosed, it may be showing 12v but its still weak, so it may be worth while trying to borrow another battery to test.

Hope that makes sense mate!


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You can trace whatever's draining your battery by disconnecting one of the battery leads and routing it through a multimeter set to measure current, you should have zero amps when the ignition's off (although your alarm may draw a little, hopefully well under an amp though).

Assuming it doesn't read zero to start with, just try pulling fuses / disconnecting things until it drops to zero.

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Just a small addendum; if you have a clock that will draw a small current as well as the alarm, as will also some radios. I had this very problem as a result of a duff radio. If you don't have a handy meter, try using a sidelight bulb or other small bulb instead like a dash bulb, with a bit of cable soldered on - if it lights between batt negative & the negative cable, then significant current is being drawn. But a meter is better. Nigel

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rover alarms/immobs have a reputation for battery draining. The old two button jobbers like the metro 200,400,800 etc.

Not sure if these were used by LR but may be worth investigation. Once they go duff they can flatten a battery in three days. :huh:

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I was working on a friends 300tdi defender last week that had the same symptons after getting altenator repaired I found the small guage wire (brown with yellow trace) on the altenator had shorted to the larger one.

this may not be any help you could have a different fault but might be worth checking to see if you have 12volts on the small guage wire going to the altenator from the dashboard with the ignition off you shouldnt have 12volts but his did

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  • 8 months later...

I had a similar problem with my Discovery. Something was draining the battery out. I found that the heating timer relay for the glow plugs was the cause. Try this by unplugging the relay and see what happens the next day, considering that the battery had enough power before disconnecting the relay. The relay is located under the bonnet, on top of the wheel arch and is held in place by a small bracket with bolt.

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You could also get yourself one of these Jobbies if you are having trouble tracking down the source of the drain as it may be a couple of circuits, also are you sure that you have not knackered the battery when the alternator went if it was fully discharged you could have buckled a plate if this is the case and they are touching the battery will 'eat it's self' easy way to test that would be to disconnect the battery measure voltage then check it in the morning clearly disconnected there should be no voltage drop.


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