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      11-07-2018, 04:54 AM   #1
HDFEBREZE
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low voltage

hi guys ill make this short and simple. when my car is running it reads about 12.7 v at the battery and about 12.9v under the hood at the jumper terminals.

one day my car didnt start and i jumped it and nothing, so i replaced the starter. everything works great. 24 hours later it does the same thing . i let it sit for a hour, than it started again. so i decide maybe its time for a new battery. buy a brand new battery. everything is good for 4 days. suddenly i notice weak start ups. so i measure the voltage while it running and notice under 13v voltage. so i replace the alternator with a new one today. run the car and test the voltage , same thing. now im stuck and i dont know what to do next. is something shorting while the car is running ?
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      11-07-2018, 07:32 AM   #2
FCobra94
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Replace the ground cable under the drivers side rocker panel that attaches to the engine block. Also clean up the ground point the cable attaches to on the frame/subframe.

I had the same issue and nothing changed after swapping out the alternator (which had a bearing on the way out anyway, so luckily it wasn't for nothing).

I've thought about adding additional ground cables as well given that the main cable I mentioned above is much more prone to corrosion, etc. given it's location. Considered adding a cable from one of the top alternator mounting bolts to the block, but haven't had a reason to mess with it just yet.
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      11-07-2018, 03:03 PM   #3
HDFEBREZE
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Quote:
Originally Posted by FCobra94 View Post
Replace the ground cable under the drivers side rocker panel that attaches to the engine block. Also clean up the ground point the cable attaches to on the frame/subframe.

I had the same issue and nothing changed after swapping out the alternator (which had a bearing on the way out anyway, so luckily it wasn't for nothing).

I've thought about adding additional ground cables as well given that the main cable I mentioned above is much more prone to corrosion, etc. given it's location. Considered adding a cable from one of the top alternator mounting bolts to the block, but haven't had a reason to mess with it just yet.
Thanks for the response, would you be able to give me the part number of those ground wires, i cant seem to find them on Realoem.com .. thanks
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      11-07-2018, 03:20 PM   #4
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https://www.realoem.com/bmw/enUS/sho...39#12427549393

https://www.e90post.com/forums/showthread.php?t=1415088

https://blog.fcpeuro.com/bmw-ground-...ry-replacement

https://www.google.com/search?q=e90+...0xQ7lOVNkA3dM:

Don't buy another OEM version...just go to the parts store and get a ground cable like this...should be like ~$5
https://www.amazon.com/Camco-47443-4...nd+cable&psc=1
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      11-08-2018, 03:07 AM   #5
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thanks a lot, ill check it out this friday and let you know how it goes.
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      11-16-2018, 03:20 PM   #6
HDFEBREZE
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Quote:
Originally Posted by FCobra94 View Post
Replace the ground cable under the drivers side rocker panel that attaches to the engine block. Also clean up the ground point the cable attaches to on the frame/subframe.

I had the same issue and nothing changed after swapping out the alternator (which had a bearing on the way out anyway, so luckily it wasn't for nothing).

I've thought about adding additional ground cables as well given that the main cable I mentioned above is much more prone to corrosion, etc. given it's location. Considered adding a cable from one of the top alternator mounting bolts to the block, but haven't had a reason to mess with it just yet.
cable on the passenger side from the frame to the engine was corroded. made a replacement and no more problems. your a life saver
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      12-04-2019, 06:39 PM   #7
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Has anyone used the $5 cable mentioned?
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