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Thread: Bad alternator connected to inoperable window switches?

  1. #1
    Join Date
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    Bad alternator connected to inoperable window switches?

    Replaced my starter yesterday - it had been failing for the last week after replacing the original 2 years ago when I did my clutch (around 205k).

    Fired the car up last night after finishing, and the battery light comes on. I checked it and it wasn't charging, O'Reilly confirmed this morning that the regulator isn't working.

    This is my fourth or fifth O'Reilly alternator this year, so I found good Bosch Remanufactured 140 amps at both FCP and eEuroparts.

    So that's the back story. (And yes, there's a decent chance the starter was never bad in the first place. Sigh...).

    ...

    I noticed that my windows and sunroof won't work when the engine is running, but they work like normal when the engine is off. Despite having the battery disconnected overnight after doing the starter, they retained auto up and down - but they won't work at all when the engine is running.

    I've never heard of our car refusing to open the windows with a non-charging system, but I can see the Germans deciding it would be a bad idea to open the windows with the alternator faulty (and I'd agree).

    I'll have the new alternator next week, and will know for sure once I replace it, but has anyone else ever experienced this?

    I'd start looking for bad grounds, but there are a couple issues with that.

    First, it seems pretty weird that it fails while the engine is running and works when it's off. So the grounds are good enough when the engine is off, but not when it's on? Or is power routed through different grounds when the engine is running vs not running? None of this sounds very likely.

    Second, it's significantly more difficult to poke around and test things while the car is running.

    I could have damaged a ground when I lowered the front subframe to get at the starter bolts, or when I bolted the starter back in. However, I didn't drop the subframe more than an inch or two, and the starter works great.

    Turn signals, hazards, headlights, and wipers all seem to be unaffected (And being safety gear, I'd expect them to work until there's nothing left).

    For everything I've done on this car with my own hands, I've never had a single electrical problem and don't even have a multimeter (Santa may have one for me in his bag this year...). So I may need to force myself to learn if this isn't "normal" operation.

    Anyway, can anyone confirm if this is actually how the car is supposed to behave or if I've buggered something?

    Thanks!

    -Josh: 1998 S54 E36 M3/4/6 with most of the easy stuff and most of the hard stuff. At least twice. 271k miles. 1994 E32 740il with nothing but some MPars. 93k miles.

  2. #2
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    are slow.
    Never buy a store brand alternator or starter. Not even for a Honda or a Toyota. They are the WORST.

    I would go to Advance Auto Parts or a auto store, and have them do an alternator/battery test with the car running.

    Perhaps your alternator isn't charging properly.
    "Be who you are and say what you feel because those who mind don't matter and those who matter don't mind."
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  3. #3
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    Quote Originally Posted by Hova View Post
    Never buy a store brand alternator or starter. Not even for a Honda or a Toyota. They are the WORST.

    I would go to Advance Auto Parts or a auto store, and have them do an alternator/battery test with the car running.

    Perhaps your alternator isn't charging properly.
    I already know the alternator is bad.

    "I checked it and it wasn't charging, O'Reilly confirmed this morning that the regulator isn't working."

    The question is whether the other behavior I described is "normal."

  4. #4
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    Just wanted to close this out and say yes. I put in a good one and no issues. And my lights are brighter than they've been since the original alternator came out.

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