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· vildside
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Discussion Starter · #1 · (Edited)
I have a 1999 540i with 120,500 miles on it. I discovered about two months ago my battery was dead one morning. I just changed the battery because it was the original battery. About a week later the new battery (a Sears Diehard, 850 CCA), was dead. I recharged it and started my long journey of electrical diagnostics. I discovered the electrical system of my car was pulling 2.20 amps when the car is off, after the battery has been disconnected overnight. The alternator is good, I have pulled every fuse, changed the ignition switch, changed the FSU (FSR), disconnected the amp and CD changer and something is still drawing 2.20 amps....can anyone help me, please?????
 

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483 Posts
You have done the troubleshooting that would typically be suggested.

This problem was asked about just recently by another member. The solution was a replacement alternator.
Check the alternator for current draw, you may have a failed diode leaking to ground.
 

· Freude am Fahren
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6,455 Posts
That's a lot of draw. Try pulling fuses after the car goes to sleep and pull the fuses one by one and check the draw with each one. That will narrow down where it's coming from.
 

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With the car running, you can unlock your OBC and use test #9 to determine the voltage being put out by the alternator. Idealy, it should be around 13.7 volts.
You can also go to Autozone where they will test your alternator for free.
What that being said, I believe the draw indicates something else going on other than a failing alt.

How can I tell if I have the High or Low OBC?

How do I unlock the OBC (Low and High)?

GL

Edit:
Moderators,

If the links above are not allowed, please edit and accept my apologies for the violation. We have a rule against this on BF.c, but we allow it if it is soley for the purpose of assisting a member.

TIA
 

· Registered
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59 Posts
Hi, in order to diagnose this problem you need to proceed systematically by removing fuses after the car's computer puts everything down in sleep mode. I will describe the procedure I followed when I had a similar problem, although if you are not comfortable with diagnostics of electrical problems then you'd better ask someone to do it for you. First, I am making the assumption that you don't have a precision clamp on DC amp. meter. If you do, then you don't need to disconnect the battery. Most people would not have this amp. meter. You would not be able to purchase it at Sears or automotive store either. Only specialized stores online sell it and its expensive. So, in the absence of an inductive clamp on amp. meter, your only other option is to disconnect the battery and connect a trustworthy amp. meter in series to the battery. Make sure connections are reliable. Having done that, you wait 15 minutes for your car to go to sleep mode - keep the trunk open. Lock your car, turn the alarm on, and push the latch on your trunk lid in to simulate closed trunk. A sign that the car is in sleep mode is that the little light by the gear shifter inside your car goes out. At this moment, your current should be below 50mA. If it is above that, you have a parasitic drain. You can start pulling fuses one after another until the current drops below 50mA. One complication is that after you pull a fuse, the car may wake up and the current draw will shoot up again. In this case, you would have to wait till the car goes back to sleep mode and continue to remove fuses. You should not open/close doors or do anything that may wake up the car while trying to diagnose this problem. I don't know how you measured 2.20A current but this what you get before the car goes to sleep mode. If you really have 2.20A of current even after waiting for 15min, you can be certain that whatever draws this current is warm to touch. I would start by pulling the fuses that supply current to the FSU, radio, CD changer, GPS computer, interior lights, etc. You'll have to be patient and use logic while doing that, but in the end you will get to the rogue circuit. I had a similar problem with my 740I BMW. It turned out to be the MK3 GPS computer in the trunk. I replaced it with a used one from ebay and it fixed the problem. CD changer also can cause problems especially when kids shove junk in that gets stuck. FSU is also a candidate. Also, a shorted diode in the alternator can do that, but I doubt that is your problem. One last note about the condition of your battery. Make sure your battery is fully charged. You say that your car was dead several times after you put a new battery in. I can tell you from experience that regular automotive batteries don't like to be fully discharged. After going dead 3-4 times they tend to stop taking much charge. If you found your car dead several times after you changed your battery, I would have someone test your battery with a battery tester. Most auto parts stores would do that for free. The battery tester checks the battery voltage when the battery is under significant load and is the only reliable method of detecting a battery that does not hold charge. Battery voltage alone is not sufficient information when comes to determining overall battery condition. Good luck and let us know what you find.
 

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I have a 1999 540i with 120,500 miles on it. I discovered about two months ago my battery was dead one morning. I just changed the battery because it was the original battery. About a week later the new battery (a Sears Diehard, 850 CCA), was dead. I recharged it and started my long journey of electrical diagnostics. I discovered the electrical system of my car was pulling 2.20 amps when the car is off, after the battery has been disconnected overnight. The alternator is good, I have pulled every fuse, changed the ignition switch, changed the FSU (FSR), disconnected the amp and CD changer and something is still drawing 2.20 amps....can anyone help me, please?????
I'm having the same exact problem. My car is pulling 2.4amps. I've actually gone through and disconnected every fuse imaginable. Nothing has solved my problem.

Right now, I'm just disconnecting the battery every time I park. I did the voltage check of loading the car, rev to 2000 and alternator output at battery was 13.86V. Autozone used their hand held device and said alternator and starter are fine. I'm curious about the diode thing. Anyone know how to check that? I keep reading that maybe it's still the alternator regardless of what autozone says. I'm almost ready to replace my alternator, BUT I'd hate to waste money if it turns out that my alternator is just fine.

How are you doing with your search? Any luck?
 

· Registered
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I'm having the same exact problem. My car is pulling 2.4amps. I've actually gone through and disconnected every fuse imaginable. Nothing has solved my problem.

Right now, I'm just disconnecting the battery every time I park. I did the voltage check of loading the car, rev to 2000 and alternator output at battery was 13.86V. Autozone used their hand held device and said alternator and starter are fine. I'm curious about the diode thing. Anyone know how to check that? I keep reading that maybe it's still the alternator regardless of what autozone says. I'm almost ready to replace my alternator, BUT I'd hate to waste money if it turns out that my alternator is just fine.

How are you doing with your search? Any luck?
Disconnecting the battery when parked while it may prevent the draw from the battery, will not recharge it especially if all your driving is just short hops from point A to B.
A good "battery float charger" will be a good investment in that it'll keep the battery fully charged and will be a good piece of hardware to have around even after you solve your issue.
 

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Good to see you James.

I came across lots of posts regarding the OP's trouble, and one of the problem was actually the CD player. Try to unplug it, leave everything else alone and see if you still have that 2.2-2.4 A loss. Actually that number (2.4A) rung a bell for me.
 

· vildside
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5 Posts
Discussion Starter · #11 ·
First of all I want to thank everyone for their advice on this issue. My latest update on my findings. I let down the front drivers' and passengers' windows. I opened the glove compartment and put a small piece of wood to hold the peg in to keep the glove compartment light off. I locked my car, turn the alarm on, and push the latch on your trunk lid in to simulate a closed trunk. I disconnected the cable from the negative battery post and waited 30 minutes. After waiting 30 minutes, I connected my amp meter between the negative battery post and the negative cable and it read 2.2 amps. I started pulling fuses and the meter kept reading 2.2 amps after pulling each and every fuse and capacitor in my car. I never put any of the fuses back in during this process, because I didn't want to wake up any modules (per mmihailov advice), so I ended up with every fuse and capacitor pulled and the meter was still reading 2.2 amps. I can't understand how every fuse and capacitor is out and the amp meter still gets a reading of 2.2 amps???? I will try the process again to make sure I didn't over look anything.
 

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?

How are the grounds? your tests IMHO indicate a short between batt and fuse box right? Any warm wires? As was indicated 2A is gonna generate some heat...

Try one of these before grabbing anything...
laser
or
cheapie

GL and something is drawing current...are all of your components working properly? test all of them...you should see something NOT working right...something will go very slow or wont' work...electricity is lazy and will take the path of least resistance...and you have somehting drawing current...window motor, lock motor something ...I am not an electrical genius like mm...
 

· vildside
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5 Posts
Discussion Starter · #13 · (Edited)
As of my last post on 02-19-2011 at 10:26 PM. I started disconnecting the ground cable from the battery every time I was parking the car for at least 4 hours. I continued this thru the middle March. On March 21st, I decided not to disconnect the ground cable from the battery and I started checking the voltage across the battery at 3 hour intervals. For 3 days the voltage was measuring at least 12.25V and I was leaving the battery connected overnight as well. From March 21st to as of this post, my battery has not drained and my car has started fine everytime. Whatever was causing the battery drain has stopped. I can't even begin to suggest what the cause was and why it stopped!!!!

April 2, 2011: I forgot to mention that on March 21st, I did unplug the flashlight that is located in the glove compartment. I will keep it unplugged.
 

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With the car running, you can unlock your OBC and use test #9 to determine the voltage being put out by the alternator. Idealy, it should be around 13.7 volts.
You can also go to Autozone where they will test your alternator for free.
What that being said, I believe the draw indicates something else going on other than a failing alt.

How can I tell if I have the High or Low OBC?

How do I unlock the OBC (Low and High)?

GL

Edit:
Moderators,

If the links above are not allowed, please edit and accept my apologies for the violation. We have a rule against this on BF.c, but we allow it if it is soley for the purpose of assisting a member.

TIA
Once I get the #9 test what do u do next?
 
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