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treyh23

*HELP* e46 318i 2000 BATTERY DRAIN?

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So I just purchased a 2000 318i knowing that it had an issue with the battery or the alternator.

Had the battery checked and charged, and it is indeed brand new and holds a charge. 

However I went to start the car 4 days after charging and it is flat, i'm not sure if its the alternator or if their is something drawing from the battery when the car is off.

Whenever i start the car, the ac is always on even when i turn it off, is that factory? 

- I have found that the 'hedgehog' final stage resistor for the ac is a common problem that draws from the battery when the car is off.

Should i take it to an auto-electrician or order the part oniline and pray?

I'm a broke uni student with an addiction to building cars if that helps.

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No, being a broke uni student doesn't help ;)

You could try unplugging the hedgehog, or pulling the fuse for that system and seeing if the battery still drains, if it doesn't then the hedgehog is the most likely culprit.

 

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You should be able to use the hidden OBC functions to get an idea of battery voltage whilst running. Test 9 will give you the info.

http://www.bmw-driver.net/forum/showthread.php?t=31204

As well as FSU some of those early climate control panels can develop a drain, later E46 have a smaller updated version. Manually turning it off before turning off the car is the way to test that.

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2 hours ago, Eagle said:

You should be able to use the hidden OBC functions to get an idea of battery voltage whilst running. Test 9 will give you the info.

http://www.bmw-driver.net/forum/showthread.php?t=31204

As well as FSU some of those early climate control panels can develop a drain, later E46 have a smaller updated version. Manually turning it off before turning off the car is the way to test that.

Cheers, battery is at 12.2v so that isnt good, just had it charged 4 days ago. Right now if i turn the headlights on, the radio dies and the dash dims. Car doesnt start. Not sure if it could be the alternator or what. Air con always turns on startup as well, sometimes turns on randomly.

Edited by treyh23

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If the alternator isn't charging, the battery light on the dash should be coming on, more likely to be a parasitic drain issue.

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10 hours ago, aja540i said:

If the alternator isn't charging, the battery light on the dash should be coming on, more likely to be a parasitic drain issue.

Cheers, i'll grab a multi-meter and get to checking fuses. 

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Did you test voltage with the car running? It's not clear.

Alternator test: start car and use positive terminal & good ground with a multimeter and you should get 14+ volts. Anything less and your alternator is on the way out.

If the above passes only then move on to parasitic loss tests: not sure what you know already but you really want to use an auto-ranging multimeter (or know how to use a manual one properly), only ever use the ground side of the battery, not the hot side (i.e put your multimeter between the battery and black cable, not the red one), make sure nothing is in an accessory socket and all doors are closed (ideally the trunk will be closed too if you can access the battery from the rear seat), establish what the draw is then start pulling fuses until it drops off. Remember you'll always have some residual draw (antitheft, ECU's, clocks, radios etc) but that should only be ~30 or 40 mA. Do NOT try and start the car, turn on the wipers or headlights or anything with an amperage that exceeds that of the fuse in you multimetre or you'll fry things and start fires.

Good luck - if a good battery is draining in four nights then you'll find the draw easily enough, it's massive.

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1 hour ago, M3AN said:

Did you test voltage with the car running? It's not clear.

Alternator test: start car and use positive terminal & good ground with a multimeter and you should get 14+ volts. Anything less and your alternator is on the way out.

If the above passes only then move on to parasitic loss tests: not sure what you know already but you really want to use an auto-ranging multimeter (or know how to use a manual one properly), only ever use the ground side of the battery, not the hot side (i.e put your multimeter between the battery and black cable, not the red one), make sure nothing is in an accessory socket and all doors are closed (ideally the trunk will be closed too if you can access the battery from the rear seat), establish what the draw is then start pulling fuses until it drops off. Remember you'll always have some residual draw (antitheft, ECU's, clocks, radios etc) but that should only be ~30 or 40 mA. Do NOT try and start the car, turn on the wipers or headlights or anything with an amperage that exceeds that of the fuse in you multimetre or you'll fry things and start fires.

Good luck - if a good battery is draining in four nights then you'll find the draw easily enough, it's massive.

Thanks for this.

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