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Steve, BMW Expert
Category: BMW
Satisfied Customers: 24187
Experience:  BMW Expert
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2000 z3 will not crank. no power at lights etc. replaced

Customer Question

2000 z3 will not crank. no power at lights etc. replaced battery, still does it. you can jump start it, turn it off and it will start.will not start after about three hours of sitting
Submitted: 1 year ago.
Category: BMW
Expert:  Steve replied 1 year ago.
Hello and welcome,
My name is ***** ***** it will be my pleasure to assist you today.
If you turn it off and wait one hour does it start?
Customer: replied 1 year ago.
ok its been sitting since 6:30am it is now 10:05 and it started right up. if i open the door and the dome light is on it fires right up if i open the door and the domelight is off it will not start, nothing electrical works at all
Expert:  Steve replied 1 year ago.

what makes the dome lights come on vs. not? time left sitting?

Customer: replied 1 year ago.
dome light automatically comes on and shuts off. if I open the door and the light is on it will start if the light is off there is no power in the car period
Expert:  Steve replied 1 year ago.
the light always comes on, and if you start the car immediately while it is still on, the car starts, but if you wait for it to go off, then the car won't start?
Customer: replied 1 year ago.
no if the light is on when I open door I know the car has juice and will start if no light I know there is no juice to start it
Expert:  Steve replied 1 year ago.

I will provide an honest answer. 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.

Thank you for your attention to the rating requirement.

What you are experiencing is called 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 (GPS, ipod dock, etc), this is the first suspect.

If there is no aftermarket equipment installed, the blower motor resistor 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.

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.

As I mentioned, the blower resistor or electric engine fan are the first items to start by checking. So simply pulling these fuses for starters and seeing if the draw persists should be an easy first step prior to a full on draw test with an amp meter or dealer power diagnosis.

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.