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Steve
Steve, BMW Expert
Category: BMW
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Experience:  BMW Expert
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what could be draining my battery in a 2004 745li. i have been

Customer Question

what could be draining my battery in a 2004 745li. i have been having problems for one solid year of my car not cranking up sometimes.the bmw company have ran numerous tests and cannot get it to duplicate so they say.so it has been in and out of the shop for the same thing fot one year.they have replaced different things in which the car runs fine for a while then it does it again.this time it happened and AAA came and plugged the battery jumper up to my vehicle and it started immediately.after that i thought that i might need a new battery,so i took it in to bmw and purchased a new battery.three days later the car would not start once again took it back to bmw.something is draining my battery and pulling power.whatever is doing this has been the problem all along.please help me i am hopeless.bmw can"t seem to find the problem i am very dissapointed in these mechaaaaaanics.this is my third bmw i have never had a single problem like this before.plllllllllease help me.......
Submitted: 4 years ago.
Category: BMW
Expert:  Steve replied 4 years ago.

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PLEASE NOTE THAT I WILL NOT BE COMPENSATED WHATSOEVER UNTIL YOU PRESS ACCEPT. NO PORTION OF THE DEPOSIT YOU HAVE PAID WILL BE TRANSFERRED TO ME UNTIL YOU PRESS ACCEPT

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Hi there,

 

Welcome to justanswer. What you are experiencing is not that rare actually (BMW has a service bulletin on this, posted below for you).

 

Your dealer should be able to find the problem, it is really not acceptable that they haven't yet found it.

 

Sometimes, when different control units go bad, they start keeping the car "awake". A closed circuit current draw is the only way to identify the problem in cases like this. This is not a difficult test, but it is time consuming. You should have this test done by your dealer or an automotive electrician.

 

Before performing a full test, I can give you a few likely places to start:

 

The two most common problems that cause a draw on this vehicle is a faulty blower regulator or faulty auxiliary cooling fan. These are the first things I suggest disconnecting, and then see if there is a still a draw on the car. If it isn't either of these, a full-on current draw test will have to be preformed, as there are no other likely culprits.

 

Please let me know if you have further questions. If satisfied with my assistance, please use the ACCEPT button so that I am compensated for my time, effort and expertise. I am not compensated whatsoever until you press ACCEPT. You must press accept or else your deposit is not transferred.

 

Cheers,

 

Steve

 

 

 

 

 

 

 

 

SI B 61 08 00

General Electrical Systems

 

 

November 2007

Technical Service

 

 

This Service Information bulletins supersedes S.I. B61 08 00 dated June 2007.

 

[NEW] designates changes to this revision

 

SUBJECT

Closed-Circuit Current Measurement

 

 

MODEL

All

 

 

SITUATION

Increased closed-circuit currents may occur permanently or intermittently, and cause the battery to discharge prematurely. The increase in closed circuit current may be caused by a faulty control unit, or by the installation of a non-approved accessory.

 

 

In a situation where a vehicle has broken down due to a discharged battery, for diagnostic purposes it is important not to disconnect the battery. This is because a control unit will be reset if the battery is disconnected. Following a reset, the faulty control unit may start functioning correctly again, making accurate diagnosis impossible.

 

To correctly measure closed-circuit current, the 50-amp clip-on probe can be used in conjunction with the DISPlus to properly diagnosis closed circuit current problems over an extended period of time. Refer to Service Information B04 07 01 for information about the 50-amp clip-on probe use with the DISPlus. A new 50-amp clip-on probe (refer to SI B04 16 04) can be used with the GT1 in conjunction with the MIB (Measurement Interface Box). Refer to SI B08 02 04 for information about the MIB.

 

PROCEDURE

 

1. NEW It is very important that any "Power management" faults stored are diagnosed and corrected and the "Energy Diagnosis" test plan carried out before the following procedure is performed.

 

 

2. Check and test the battery using the BMW Battery Tester. Refer to SI B 04 25 02 for information about the BMW Battery. If necessary, recharge or replace the battery.

 

 

3. If the battery is installed in the trunk, open the trunk and turn the lock to the locked position using a screwdriver or similar (simulates the trunk lid being closed). The hood must be closed. If the battery is installed in the engine compartment, open the hood and pull the front lid contact switch fully up and lock in this position (workshop position, simulates the front lid being closed). The trunk must be closed.

 

 

4. With the exception of the trunk / hood above, all other doors / lids must be closed.

 

 

5. In order to simulate normal closed-circuit conditions:

 

 

- Turn ignition on and activate all electrical consumers, including any accessories. Turn ignition off. In some cases a drive cycle may need to be carried out in order to duplicate a closed circuit current problem.

 

 

- Open and close the driver's door (simulates somebody getting out).

 

 

- Lock the car, arming DWA if this is installed.

 

 

 

6. In general, closed-circuit current consistently over 50 mA must be investigated. Depending on the vehicle's equipment, closed-circuit current by vehicle model is approximately as follows:

 

 

E31 50 milliamps after 16 minutes

E32 50 milliamps after 16 minutes

E34 40 milliamps after 16 minutes

E36, Z3 30 milliamps after 16 minutes

E38 50 milliamps after 16 minutes

E39 40 milliamps after 16 minutes

E46 40 milliamps after 16 minutes

E60, E61, E63, E64 40 milliamps after 60-70 minutes

E65, E66 40 milliamps after 60-70 minutes

E53 40 milliamps after 16 minutes

E70 40 milliamps after 60-70 minutes with TCU (30 minutes without TCU)

E83 40 milliamps after 16 minutes

NEW E90, E91, E92 40 milliamps after 60-70 minutes with TCU (30 minutes without TCU)

E85 40 milliamps after 16 minutes

E52 50 milliamps after 16 minutes

 

 

 

 

 



Edited by Steve on 9/16/2010 at 2:19 AM EST
Steve, BMW Expert
Category: BMW
Satisfied Customers: 19741
Experience: BMW Expert
Steve and 7 other BMW Specialists are ready to help you
Customer: replied 4 years ago.

HI, STEVE I HAVE SPOKEN WITH BMW AND THEY ADVISED ME THAT I NEED AN ALTERNATOR . I DON'T UNDERSTAND WHY THIS PROBLEM WAS NOT DETECTED WHEN I REPLACED THE BATTERY 3 DAYS AGO. I REALLY DON"T FEEL LIKE THEY KNOW WHAT THEY ARE DOING. I GAVE THEM YOUR RECOMMENDATION I DON'T KNOW WHAT TO DO.

Expert:  Steve replied 4 years ago.

If the alternator indeed tested bad then it will need to be replaced. However, they should be able to identify a current draw if there is one, and it sounds like you may have one, so I would make sure they do the appropriate test.

 

 

 

Customer: replied 4 years ago.
thank you so much steve i appreciate your rapid response.you are a lifesaver. i really feel like they are pulling at things and not fixing the underline problem.
Expert:  Steve replied 4 years ago.
you are welcome.

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