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Discussion Starter #1
I have a bmw 320ci 2002, Whenever i leave my car off for about 3-4 days i get a "dead battery". I have changed my battery twice with brand new ones, I have taken the car to a auto-electrician left it there for a few days they couldn't find anything wrong with it.

Then took the car to BMW for a service and told them the problem, they told me it was a heater fan module resistor that was faulty (heater fan not turning off) got that changed but im still having the same problem.

Any suggestions ? Thanks
 

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get a voltmeter.
measure the voltage at the battery with the car off. Should be at least 12.5v.
start the car.
measure the voltage at the battery. should read at leas 14v. If it does not read 14v+, then you should start checking the charging system. Check for corrosion on terminals, check for lose connections, check the alternator.
 

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I got the results from my last test done (not long ago): JUMP STARTED - Voltage : 10.40V, Charging system test - no problems 14V and drain test 2.11A.

The battery terminals still appear to be 'like new' all solid strong connections. BMW and the auto-electricians said that the alternator was fine theres nothing wrong with it.

Thanks.
 

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If the battery dies after sitting, it can't be the alternator.
There must be an intermittent parasitic draw, when the shop had the car, it was OK.

You need to measure the electrical draw, 500 mA is the limit.
Keeping the multimeter connected between the negative battery terminal and the disconnected cable, pull the fuses one by one.
That way you can find which circuit is involved.
 

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to add to whats been said when you do the draw test keep the trunk open and use a screw driver to latch it. also do this with the passenger door and open the glove box to access the fuse box. wait for the car to go to sleep about 30min test across each fuse and find with one has millivolts. the fuse that has voltage on it that is not either 12v or 0 is your draw. look on the paper to find which fuse that goes to and poof you have your draw. if it is a module then pulling the fuse could temporarily reset it and then you will be chasing your tail.
 

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I got the results from my last test done (not long ago): JUMP STARTED - Voltage : 10.40V, Charging system test - no problems 14V and drain test 2.11A.

The battery terminals still appear to be 'like new' all solid strong connections. BMW and the auto-electricians said that the alternator was fine theres nothing wrong with it.

Thanks.
That's really low.
 

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I got the results from my last test done (not long ago): JUMP STARTED - Voltage : 10.40V, Charging system test - no problems 14V and drain test 2.11A.

The battery terminals still appear to be 'like new' all solid strong connections. BMW and the auto-electricians said that the alternator was fine theres nothing wrong with it.

Thanks.
10.4V. Your battery is done. Start by replacing it first.
2.11A? Is that parasitic? if so, you have a short somewhere. Follow the steps lszlszx suggested to find out what's causing the problem.
 

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BE CAREFUL HERE.

Fully charged battery is 12.6 Volts @ 68F temp after surface charge is removed.
If the battery Voltage as 12.0 Volts @ 68 F temp, the battery is 75% discharged.
11.9 Volts is considered a fully discharged battery.
The above also assume there is not a weak cell or internal battery connections. A load test needs to be performed in ADDITION to checking the battery surface Voltage.

Proper charging Voltage is 13.5-14.5 Volts.

If you REALLY have a 2+ Amp current draw after 18 minutes, this is your problem. BUT BE CAREFUL, the current draw will be high until the vehicle modules go to sleep.

As as mentioned, you need to make sure the car THINKS it is fully closed up, then you need to see what the current draw is after the cars modules go into standby. Unfortunately, I do not have baseline values handy for a "known good" E46, but expect the standby current draw to be 200mA or less would be my guess. I would probably expect 150mA or less, BUT if the clown nose is blinking and/or the vehicle has an alarm system with motion dectector(s), the values I stated may be a bit low??
 

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Discussion Starter #9
thanks everyone for the help, it actually turned out to be a faulty CD stacker in the boot which was drawing a huge amount of current when the car was off.
 
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