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Steve
Steve, BMW Expert
Category: BMW
Satisfied Customers: 24115
Experience:  BMW Expert
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when starting in mornings it seems like battery is flat and

Customer Question

when starting in mornings it seems like battery is flat and lights on dash go out it is starting and once running is fine even if u turn of and restart battery tested and is fine
Submitted: 3 years ago.
Category: BMW
Expert:  Steve replied 3 years ago.

hello

 

what do you mean by "lights on dash go out it is starting "

 

how does it start? I don't understand what you are experiencing?

 

do you mean that the lights dim while starting?

Customer: replied 3 years ago.

it kind of stutters like flat battery dash lights stutter with it also clock and m.p.g etc all go to zero and need resetting had battery checked on 2 testers all fine

Expert:  Steve replied 3 years ago.
Has the battery been tested in the morning to see what condition it is in after sitting?
Customer: replied 3 years ago.

no i had to drive 2 miles to garage

Expert:  Steve replied 3 years ago.
You symptoms are consistent with parasitic draw. This is actually somewhat common.

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, this is the first suspect. After that, the blower motor resistor/speed controller and also the electric engine fan (if fitted) are common items that cause this drain. Beyond these items though, it could be ANY component on the car.

In order to determine the cause of this drain, 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. Dealers also have special equipment they can use to pinpoint drains like this.


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