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Discussion Starter · #1 ·
Recently on one of my more spirited drives I came across a large pothole on a back road and hit it. There was no cosmetic damage however, I noticed that there is now a red battery light on my dash that will occasionally go away if I hit another bump. Thinking perhaps I snapped the accessory belt I checked if I had power steering, which I do. The battery is only 3 months old so I ruled that out. The alternator is the next thing that comes to mind, however after letting it sit for about 30 minutes idling I turned the car off and tried to crank it over expecting the battery to be dead, but it started just fine. Anyone have any idea what's broken that's causing this? Thanks for the replies in advance!
 

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Discussion Starter · #3 ·
Loose battery cable?

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I pulled over and checked both connections on the battery, disconnected the negative and the car subsequently died. Only to turn over just fine after I reconnected the battery, so I don't think the cable is the culprit.
 

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2016 340i xD 6-spd
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Pull up on your battery clamps--many have tightened them up only to find they're not sitting tight on the battery terminal. They make spacers for that.

Usually red bat light means alternator. Mine flashed on and off for a week or so until it stayed on and I wasn't getting any power from it at all. Measure the voltages you're getting from the car. Should be 12.5 ish when it's off, and 14V when on. Use multimeter or the cluster display--

...and look at major grounds, and make sure the +terminal under the hood is tightened up too.

Hope you don't need more than an alt. Many here just do the voltage regulators, but of those who do only that, some % seem to get the wrong VR. I just got a rebuilt Bosch...easy diy.
 

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E30M3 Race F10 535 R1150Rt M Coupe
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Check ALL the battery cable connections: Back of alternator, on the starter, at the jumping post.

Most of all, I'd be checking both sides of the ground cable and the motor mount arm....
 

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Don't just guessing. Use a voltmeter to check if the alternator outputs 14v when engine running.
 

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Discussion Starter · #8 ·
After driving the car a bit further this morning I noticed a rather strong smell of burning metal or rubber or something like that. I immediately went back to the garage and came to the conclusion that my alternator was in fact toast. I had a refurbished bosch alt delivered only a few hours later. I installed it, and it seems to have fixed my issue. Thanks for the replies guys!
 

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Discussion Starter · #10 ·
Wow, what can a deep pot hole do to damage the alternator? Might be the big shock broke the diodes bridge circuit.
From what I can tell, the alternator I pulled out was OEM so I think a replacement has been long overdue. Perhaps the jolt was just the straw that broke the camel's back so to speak.
 
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