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Steve
Steve, BMW Expert
Category: BMW
Satisfied Customers: 24427
Experience:  BMW Expert
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I have a 2006 petrol engined BMW X3,which I have owned from

Resolved Question:

I have a 2006 petrol engined BMW X3,which I have owned from new.
On 4 or 5 occasions during the first 3 years the battery would go flat overnight although it had been used the day before.It was under guarantee and BMW would provide a rescue service which basically consisted of a jump start--the mechanic couldn't find a problem and advised having it checked by Benham,the local dealer--they never found a problem either and after the first 2 or 3 occasions wanted to charge for the investigation.
Over the years the problem has got much worse so I now have to put the battery on charge every night to ensure the car will start in the morning.
Incidentally if I forget to charge the battery it only takes about 30 minutes of a trickle charge to be able to start the engine.which seems ridiculous after the battery has gone dead.
Submitted: 3 years ago.
Category: BMW
Expert:  Steve replied 3 years ago.
is the vehicle still on the original battery?
Customer: replied 3 years ago.
No
I have had at least 2 new ones in an effort to improve things but whenever the battery and alternator have been checked they are in good order
Expert:  Steve replied 3 years ago.

I will provide an honest answer and am doing so in good faith. I trust this will be appreciated. Please remember that a low rating PUNISHES me for being honest and that I receive nothing for my time until a positive rating is clicked.

 

 

the problem is not the battery

 

the problem is that you have a parasitic draw. This is actually somewhat common and your dealer should have been able to resolve this easily with some testing.

 

There is some component on your vehicle that is draining power overnight while the car is supposed to be off.

 

If you have any kind of aftermarket equipment installed (GPS, ipod dock, etc), this is the first suspect.

 

If there is no aftermarket equipment installed, the blower motor controller is by far the most likely culprit. Also, the electric engine fan is also somewhat common.

Beyond these items though, it could be ANY component on the car.

 

In order to determine the cause of this, you will need to unhook the negative battery cable and hook up an amp meter and measure draw after the car is locked and has sat untouched for 20min (this is when it is supposed to be in "sleep mode"). If there is more than about 50ma of draw at this point, you will need to pull fuses one by one until the draw stops. Whichever fuse stops the draw is the problem circuit.

 

If you are not familiar with using this equipment or performing this type of test, you should have it carried out professionally, any BMW specialist or auto electrician will be familiar with this testing.

 

BMW dealers also have special equipment they can use to help identify the cause of this, so this is a second option, besides the above test.

 

Sorry if you were hoping for a different answer, please don't shoot the messenger - I can only give the honest answer, which I have. Please remember that a low rating PUNISHES me for my honest and prompt response, and I receive nothing for my time and answer until a positive rating is clicked.

Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you. Best wishes with your vehicle

 

 

 

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