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Old 03-21-2013, 05:44 PM   #1
Odyss3us
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Battery Draining, Can't Find Problem

Hi,

I have a 2000 323i, manual. About two months ago, after a really cold -30ish C night, my car wouldn't start. The battery was really old so I replaced it and the car started fine for around 2 weeks. Then the battery died. I jumped the car and drove it for half an hour to charge it back up.

I did a series current test. The car draws 110-120 mA when its asleep. When I pull out the 50 A electric fan (#37), the current drops to 50-56 mA. When I pull out the rear window heater fuse (#68) the current drops to around 6 mA. Also the current rises briefly (only lasts half a second) by about 5-10 mA every few seconds which I assume is probably some computer turning on, doing something and going back to sleep?

So anyway, once the new battery died I did the series current test and found that the car had been drawing 110-120 mA. I read somewhere that BMW's spec is 40 mA, so after turning the car off I pulled the electric fan fuse so that the car would only draw around 50 mA. But the battery still wouldn't keep a charge and I had to jump it 2 more times. After the jumps I would run the car for more than half an hour, but the battery would slowly and surely run down from 12.5 V to 11.9 V and then need to be jumped again after a few days.

My alternator appears to be fine. When I'm running the car the voltage across the battery is 13.9-14.1 V. There's been no warning lights or anything else weird happening with the electrical system. Is it possible that the alternator is supplying the right voltage but not enough current to properly charge the battery?

I thought maybe I just had a bad battery and exchanged it yesterday for a new one. I put it in and ran the car for an hour. This morning I when I went out to start it I did the dashboard voltage meter thing and the battery was already at 12.1 - 12.2 V. This was again with the electric fan fuse pulled so the car should only be drawing 56 mA. Drawing 56 mA is higher than spec but not much. Shouldn't the battery last weeks before it needs to be jumped again?

When I did the series current test I couldn't connect the DMM leads without disconnecting the battery. Do you think by disconnecting the battery, hooking up the DMM and reconnecting that I might have reset something that would have been drawing power but didn't do so in the test because it was reset?

Also is there something wrong with my electric fan and rear window heater? They shouldn't be drawing anything when the car's off right? Do you think I should replace them?

Right now the car is sitting with the electric fan fuse and the rear window heater fuse pulled so hopefully it is only drawing ~6 mA.

Do you guys have idea what's killing my battery?
Thanks
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Old 03-21-2013, 05:58 PM   #2
taibinhvuong
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No idea, all I can think of is you have some kind of short or grounded that drained your battery, since you already had the electric fan and the rear window heater fuses pulled, just wait and see the battery is still drained or not and then go from there.
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Old 03-21-2013, 06:00 PM   #3
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OP, you replace the FSR yet?
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Old 03-21-2013, 06:15 PM   #4
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I've seen on the X5 forum that most battery drains is bc of a bad final stage resistor
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Old 03-21-2013, 07:09 PM   #5
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I don't think I have short anywhere as there would always be current flowing and I would have seen it in the series current test.

No I haven't changed the FSR yet. When I found that the fan was drawing 60-70 mA when the car was off I figured that was the reason the battery was dying. But now I know it isn't as I've been pulling its fuse. Also I don't have any FSR symptoms that I know off.

I'll remove the FSR and see if that helps. (I'm assuming I can drive the car without the FSR as long as I don't mind not having climate control right?)
Also is it normal / acceptable for the electric fan to be drawing 60-70 mA and the rear window heater to be drawing 50-56 mA when the car is off or should I look into those as well?

Thanks again
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Old 03-21-2013, 07:42 PM   #6
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I think the spec for e46s is about 400 mA after the car has entered sleep mode, not 40.
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Old 03-21-2013, 08:51 PM   #7
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I highly doubt the spec is 400 mA. I would guess <=50.
OP. You need to find out all consumers on those circuits. Just because the fuse label says rear window defroster doesn't mean that's the only thing on that circuit. If you can access good quality OE schematics that would help.
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Old 03-21-2013, 11:10 PM   #8
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I'm pretty sure nothing else is on the electric fan circuit as I can disconnect the fan right at the connector on the fan and this has the same effect as pulling out the fuse. Although I suppose some other consumer could be wired in series with the fan and disconnecting the fan breaks the circuit to that consumer as well. This seems unlikely to me but I'm sure others will know better than I do. I haven't looked at the rear window heater but I have a Bentley manual so I'll take a look through the wiring diagrams.

From what I've read about others' FSR problems, it doesn't really sound like my problem. Everyone else seems to report having symptoms like the interior fans randomly turning on when the car is off and things like that. In my case the battery seems to die fairly linearly and regularly over the course of a few days after being jumped. I've never had any weird behaviour from the fans and I've never seen them turn on by themselves before. Also in my case the battery slowly but surely dies over the course of a few days while if it was the FSR turning on in the middle of the night, wouldn't that just randomly kill the battery in a few hours?

I'm still going to take the FSR out tomorrow when I have more time. I'll get back to you guys with results when I have them.
Thanks again.
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Old 03-23-2013, 04:59 PM   #9
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Hi,

So I took out the FSR 30ish hours ago then drove around for an hour to put a full charge on the battery. I've been checking the battery voltage every few hours and it seems to be holding steady so I guess that was the problem. Thanks guys.

I still have a few more questions:

Where's the best place to order parts from if you live in Canada?

I dropped the top screw of the stepper motor when I was putting it back and I'm not sure if it fell into the center console area or into the cavity where the heatsink part of the FSR sits. Should I be worried about it rolling into something important or shorting something out?

My electric fan will still be drawing 60-70 mA even with the car off and whatever is on the rear window heater circuit will still be drawing 50-56 mA with the car off. Should I replace the electric fan and look into whatever is on the window circuit?

Does anybody know how the FSR works / whats inside? Everyone knows what it does but I can't find any information on it in my Bentley manual or online. I'm in school for electrical engineering so I'm gonna take it apart and see if I can figure out what makes it tick.

Thanks guys.
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Old 03-23-2013, 06:49 PM   #10
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Quote:
Originally Posted by Odyss3us View Post
Hi,
Does anybody know how the FSR works / whats inside? Everyone knows what it does but I can't find any information on it in my Bentley manual or online. I'm in school for electrical engineering so I'm gonna take it apart and see if I can figure out what makes it tick.

Thanks guys.
The FSR contains several different pathways with different resistances. The climate control module just picks combinations of them to control the blower motor speed. The device would seem to be in series with the blower motor. So by changing it's resistance, you change the voltage drop across the motor, thus controlling its speed. It should be quite simple on the inside, if you can get to it. However, the circuit board is covered with resin on one side (indestructable). Hopefully the resistors have been left exposed on the other side for heat transfer purposes. You'll have to cut it apart.

Last edited by WDE46; 03-23-2013 at 06:51 PM.
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Old 03-23-2013, 07:30 PM   #11
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This is why I say see sig, do it all. Prevents these problems happening in the first place.

Follow the links in my sig, and you'll never experience a problem.
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Old 03-23-2013, 08:15 PM   #12
taibinhvuong
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Originally Posted by Odyss3us View Post
Hi,

So I took out the FSR 30ish hours ago then drove around for an hour to put a full charge on the battery. I've been checking the battery voltage every few hours and it seems to be holding steady so I guess that was the problem. Thanks guys.

I still have a few more questions:

Where's the best place to order parts from if you live in Canada?

I dropped the top screw of the stepper motor when I was putting it back and I'm not sure if it fell into the center console area or into the cavity where the heatsink part of the FSR sits. Should I be worried about it rolling into something important or shorting something out?

My electric fan will still be drawing 60-70 mA even with the car off and whatever is on the rear window heater circuit will still be drawing 50-56 mA with the car off. Should I replace the electric fan and look into whatever is on the window circuit?

Does anybody know how the FSR works / whats inside? Everyone knows what it does but I can't find any information on it in my Bentley manual or online. I'm in school for electrical engineering so I'm gonna take it apart and see if I can figure out what makes it tick.

Thanks guys.
Although it could highly be the FSR, but in usual, a resistor or FSR tends to fail open (higher resistance) rather than fail short (lower resistance) and unlikely be caused the drainage of the battery especially when the ignition key is out (open circuit) unless the control module is malfunction.

May be something that I don't understand, someone can jump in and explain thoroughly detail to me that will be highly appreciated.

I think to be hundred percent sure that the problem is the FSR or the control module, you can try this: with car off and ignition key out, you can use the digital amp meter and hook it in series with the battery path (disconnect the negative cable from the battery and insert the amp meter between the battery negative post and the ground) and measure the amperage readings with and without FSR (disconnect FSR) then compare the 2 readings, if the amp reading with FSR is higher than the reading without it, then you have a drain from FSR, if the readings are the same, I see no reason that the FSR could cause the drainage.

Important note: never start up the car with this kind of amp measuring hookup, otherwise it could cause damage to the meter or in worst case could cause fire.
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Old 03-24-2013, 12:01 AM   #13
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I think to be hundred percent sure that the problem is the FSR or the control module, you can try this: with car off and ignition key out, you can use the digital amp meter and hook it in series with the battery path (disconnect the negative cable from the battery and insert the amp meter between the battery negative post and the ground) and measure the amperage readings with and without FSR (disconnect FSR) then compare the 2 readings, if the amp reading with FSR is higher than the reading without it, then you have a drain from FSR, if the readings are the same, I see no reason that the FSR could cause the drainage.
I tried doing a closed circuit current measurement and the only things that were drawing any current were the electric fan and the rear window heater circuits. When I pulled the fuses for those circuits the current dropped to 6 mA. That being said I had to disconnect the battery completely to put in my multimeter and I've heard you should insert the multimeter without breaking the circuit because it might reset something that is drawing current and you won't see it when you do the test. I tried to do this but its pretty hard without the proper leads to connect to the battery. Anyway even with the short circuit test showing only 6 mA my battery kept dying so obviously either what was killing the battery was intermittent and it just didn't happen when I did the test or whatever it was was being reset when I disconnected the battery.

My battery seems to be holding its charge since I removed the FSR but I'm still pulling the electric fan and rear window heater fuses when I'm not driving because I don't think they should be drawing 65ish mA and 55ish mA respectively, when the car is off. This seems to be on the high side to me.

Can someone please check if their car is drawing that much current on those circuits?
I'm still wondering if I should replace the electric fan?
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Old 03-24-2013, 02:15 PM   #14
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Originally Posted by Odyss3us View Post
I tried doing a closed circuit current measurement and the only things that were drawing any current were the electric fan and the rear window heater circuits. When I pulled the fuses for those circuits the current dropped to 6 mA. That being said I had to disconnect the battery completely to put in my multimeter and I've heard you should insert the multimeter without breaking the circuit because it might reset something that is drawing current and you won't see it when you do the test. I tried to do this but its pretty hard without the proper leads to connect to the battery. Anyway even with the short circuit test showing only 6 mA my battery kept dying so obviously either what was killing the battery was intermittent and it just didn't happen when I did the test or whatever it was was being reset when I disconnected the battery.

My battery seems to be holding its charge since I removed the FSR but I'm still pulling the electric fan and rear window heater fuses when I'm not driving because I don't think they should be drawing 65ish mA and 55ish mA respectively, when the car is off. This seems to be on the high side to me.

Can someone please check if their car is drawing that much current on those circuits?
I'm still wondering if I should replace the electric fan?
You can go ahead to hookup the digital amp meter the way I described, yes, it will break the circuit, if you afraid it might reset something and you may not be able to read the current, then you can insert the key and turn it to position II (warning: do not start the car), leave the key there for few minutes, this should get everthing back on again, and then you can withdraw the key and proceed to the measuring steps.

Edit: you can also leave the key in position I with FSR in place, and measure the different currents with fan on (set at lowest setting) and fan off to see what is the minimum current that the fan draws, and compare this current to the one that you measured above with key out of inigtion lock, and perhaps you may get some ideas about FSR being draining current or not.

Or post the readings here so that we can analyze together.

As far as the current readings of the electric fan and rear window heater, I don't think that you need to concern at all, 65mA is just 0.065A, too small of a current drawed that can hardly drain out your 100A/hr battery.

Last edited by taibinhvuong; 03-24-2013 at 03:23 PM.
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Old 05-15-2015, 06:11 PM   #15
timmadera
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I almost similar problem. My battery drains the fan comes on randomly with key out, I charge battery with charger. tool to auto parts store tested alternator and battery in circuit. Drive car ok then park come back few hours later and the battery flashing lights and not starting. not sure where this FSR is in car?
I can try put meter in circuit but waht is the draw with nothing on? if one of the cells in battery is bad how do I check it.?

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Old 05-15-2015, 10:13 PM   #16
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Do you have any aftermarket additions to the electrical system? I imagine that something is keeping the computer running while the car is supposed to be sleeping, whether it is an FSR, ignition, cluster, etc. You might try getting to the K-Bus bar near the fuse box where all the K-Bus circuits come together and remove one circuit at a time to see if a device on the bus has failed and could be preventing a proper shutdown of the computers.

To test the sleeping current, I'd recommend placing a jumper in parallel with your multimeter, all in series with the battery circuit for a few minutes to let the car go to sleep before removing the jumper to allow an accurate current measurement using the lower scale on your multimeter.
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Old 08-23-2015, 01:08 PM   #17
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I'm trying to track down a drain now. I have about a 700mA draw...
How do I fool the car to think that the passenger door is closed while I pull fuses? I don't see an old fashioned plunger in the door jam.

Thanks for any help!
Mike
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Old 08-23-2015, 06:45 PM   #18
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I had an ordeal with a battery drain that took almost 3 years to find. Two batteries two fsr's countless hours trying to find a parasitic draw. Turned out to be the single biggest circuit in the car on fuse 37. Details here.

http://forum.e46fanatics.com/showpos...6&postcount=68

For fun read the thread from the start. It also covers anything else that might cause a drain as we tried everything.
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Old 08-23-2015, 07:05 PM   #19
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Thanks, already read the
Disconnecting the fan connector did nothing...not warm, but continue to check.

Thanks for the reply.
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Old 08-26-2015, 12:27 PM   #20
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I'm trying to track down a drain now. I have about a 700mA draw...
How do I fool the car to think that the passenger door is closed while I pull fuses? I don't see an old fashioned plunger in the door jam.

Thanks for any help!
Mike
I guess I'll just pull the interior lighting fuse(s).
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