Battery Problem on 2001 BMW 530i

I just got a 2001 530i and something keeps draining my battery. Has anyone experienced this with their car? I replaced the battery with a new one and 3 days later it is dead. What could be the problem? Any info would greatly be appreciated!

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3 answers 5 comments
There is a control/relay/resister unit related to the cabin air circulation or AC fan Blower system. When it goes bad, it will suck down your battery in no time at all while the engine is off and the key is removed. It is located on the right hand front passenger "feet" area on the left side (shin high). Remove the thin strip of carpeted trim. You will find a plastic air box unit just above the carpet line. It is mounted to the drive train tunnel. That is the best way to describe the location. The unit has a bunch of aluminum studs protruding from it and these studs dissipate heat while the air is passing by it (when installed). You have probably noticed problems with your automatic low and high fan blower speeds and this is an indication of the problem. A good parts guy can read this and sell you the right part. It was not hard to change. 40 minutes. Brian Mac
Start with any thing not BMW does the car have an aftermarket stereo, amplifier, or burglar alarm check for power drain there first. Disconnect the battery and put an amp meter in line with the power cable look for the battery draw, it shouldn't be more than .2 Amps. Start pulling the fuses out one at a time and see pulling which fuse causes the battery draw to go away. When you locate which fuse makes the draw goes away then its down to checking the things protected by that fuse.
Have you charged and tested the battery just to make sure you haven't got a bad battery.
Without looking at it, my mechanic said it was probably the alternator. The dealership I bought it from came by and took it to their shop to see what is wrong. Hopefully they will be able to figure it out.
I don't have any aftermarket items in the car. It is all basically stock.
Just got off phone with shop mechanic. They said they had to replace the alternator.
I have seen Bosch alternators do this before. Disconnecting the alternator they probably saw the draw on the battery go to zero. Hope it wasn't too expensive.
I have the same problem I changed 2 alternator in 3 weeks , and today my car died on my driveway. If you find what was the problem with your car, please let me know, i am desperate cause I spend a lot of money and the same problem is coming back over and over again. Please send me a mesage to simonamathe@yahoo.com. Thank you.
I had the same problem. I found that the fan inside the car was not turning off. Turn the car off and listen for the fan to keep runing.
I had this problem and it was resolved by a really good mechanic in DE. You have to replace a part called the Ënd Unit Resistor. It works!
Yes, it was a bad altenator.

JCM