BMW Questions? Ask a BMW Repair Expert for Answers.
It sounds like you have something that is draining the battery. For example something remains on or something is shorted.
This is called a parasitic draw. This can be tough to find. You need to be failure with the use of an amp meter and have access to all of the vehicles wire diagrams.
Your best choice may be to take it to a dealer.
A few common causes are the final stage resistor for the blower, or the auxiliary fan in front of the condenser.
These can be checked by unpluging them while monitoring the current draw.
You place your meter in the milli amp scale. Connect it in line of the negative cable.
Click the lock on the trunk lid to turn off the trunk light. Leave the front doors open while doing this and click those locks shut too. You can do this with a small screw driver.
Let the vehicle go to sleep -this takes about twenty minutes. Normally when the light next to the shifter is out it is asleep.
Now take a look at the meter. A normal draw is around 50 milli amps or .05
If it is more then that then you can go to the individual components and unplug them
or pull fuse one by one until you see the amperage draw come down.
I hope I have helped you.
you are a genius! thanx so much