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Steve, BMW Expert
Category: BMW
Satisfied Customers: 25414
Experience:  BMW Expert
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Bmw 645ci 2004 The car battery power goes up and down. Then

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Bmw 645ci 2004
The car battery power goes up and down. Then the warning lights appear everything from battery power to transmission fault. Then car shuts down. After a while it will start again.
what do you mean by "the battery power goes up and down" ?
Customer: replied 2 years ago.
The window is slow the wipers are slow. The centre console display screen starts to flash the warning lights come on ie. Low battery warning active steering transmission fault. The car then shuts down. And will not start. If left switched off for 10 minitues it will start again. But the problem is still there

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.

the problem is almost certainly the alternator playing up intermittently.

simply having the alternator tested when the issue is not present will not detect the issue.

system voltage will need to be tested when the issue presents itself to verify that alternator output is low.

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.


I can see that you have rated my answer as "bad"

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was some part of your quesiton not answered? I believe the question was answered. If so, please change the rating to OK / 3 stars or higher so that I am not PUNISHED for trying to help

Customer: replied 2 years ago.
Could there be a problem being created by the rear fog light. It really seems to be an issue. If it is working the phlegm goes away


is there a reason you rated my answer as bad? This PUNISHES me for answering the question as best as possible based on provided information.

Please kindly change your rating to OK / 3 stars or higher to ensure I am not PUNISHED for taking time out of my day to help you as best as possible.

a fog light is not powerful to cause a car-wide voltage issue. you can remove it and see if anything changes, but the chances are slim to none

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