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Old 04-22-2013, 03:25 PM   #1
bimmere30
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alternator problem? not charging battery?

what could be the problem i have a 1991 bmw 318i and i replaced the alternator since i received shit load of lights on the dash and car stalled on the road. The battery is one year old, voltage regulator for alternator looks good,
i give it a boost after replacing alternator, everything starts and runs, alternator belt runs but the car stalls after a minute everytime and i get dash lights as well. Is the alternator not charging the battery?
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Old 04-22-2013, 04:16 PM   #2
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Don't guess: test it with volt meter. They're under $10. You should see around 13.5V when the vehicle is running, 12.5V when it's off.

General things to check: ground point at the battery in the trunk where it connects to the chassis, and the ground from the chassis to the block just behind the alternative at the bottom of the engine. Poor grounds have caused many a wasted day fixing poor running e30s.
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Old 04-22-2013, 05:16 PM   #3
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i checked the voltmeter dips below 10V and then stalls, fyi my battery light doesn't light up when i put the key into ignition on position. could it be the exciter wire that connects to the cluster battery bulb? some guy said if the battery bulb goes out the alternator doesn't charge.
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Old 04-22-2013, 06:33 PM   #4
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I think that was only on the early models, not the later ones but it might be worth a shot. They all use the same bulb so swap your brake lining light over (lawl) and try it out.
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Old 04-22-2013, 06:33 PM   #5
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If it is the alternator, the battery ground at the engine to the chassis could be the culprit, FYI.
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Old 04-22-2013, 06:56 PM   #6
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Check your positive connection on the alternator. If the battery drains within 1 min to 10 volts that's like not having an alternator connected at all. With the engine off check the voltage across your batt terminals. Then check the voltage across the power terminal on the back of the alternator and the engine ground post. The voltage should be the same.
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Old 04-22-2013, 07:07 PM   #7
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i checked the ground strap everything is secure still no charge the alternator belt is tight as well the wires are in the correct places and tight as well, all the battery connections are tight as well. the light bulb was replaced for the cluster thingy as well. i do not know why its not charging.

Last edited by bimmere30; 04-22-2013 at 07:08 PM. Reason: added more info
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Old 04-22-2013, 07:47 PM   #8
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Quote:
Originally Posted by bimmere30 View Post
fyi my battery light doesn't light up when i put the key into ignition on position. could it be the exciter wire that connects to the cluster battery bulb? some guy said if the battery bulb goes out the alternator doesn't charge.
This is true...

The bulb completes the circuit for the exciter... replace the bulb (or at least verify that it is working) it needs to light up and you turn on the ignition otherwise it will cause the Alt. not to charge.

EDIT: just seen that you replaced the bulb.

At this point it's time to start digging... jump the exciter wire directly to 12V and see if the alternator start to charge, if it doesn't I'd say that the one you put in (if used) isn't working.
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Old 04-22-2013, 08:06 PM   #9
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does anyone have a spare alternator, i don't remember if the one i had was working condition.
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Old 04-23-2013, 09:58 AM   #10
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before you go through the trouble, why not just jump the exciter first and see what happens.
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Old 04-23-2013, 12:10 PM   #11
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I'm pretty sure this problem with the bulb was fixed in the 88+ electronics guys. It's even documented in the electrical schematics.

While the ground straps are secure, it doesn't mean they're making good contact, I should have been more specific. Remove them, clean up the contact patch and try again.

I have a spare alternator.. If you were closer I'd gladly let you try it but I'm in Ottawa.
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Old 04-23-2013, 07:09 PM   #12
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still no luck

i replaced the voltage regulator with an aftermarket one and still doesn't work, the abs and battery light stay on when the car is started. It does the same thing shakes then stalls out.
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Old 04-23-2013, 07:10 PM   #13
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how do i jump the exciter?
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Old 04-24-2013, 11:31 AM   #14
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I'm pretty sure this problem with the bulb was fixed in the 88+ electronics guys. It's even documented in the electrical schematics.

While the ground straps are secure, it doesn't mean they're making good contact, I should have been more specific. Remove them, clean up the contact patch and try again.

I have a spare alternator.. If you were closer I'd gladly let you try it but I'm in Ottawa.
You're right, seems like the later clusters have a resistor parallel to the bulb to allow charging if the bulb burns out.

That said, I would still manually jump the exciter wire in case there is an issue in the harness, etc.

OP, it's the blue wire going to the alternator as seen here:

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Old 04-24-2013, 06:26 PM   #15
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finally works, i had to charge the dead battery a bit for the alternator to work.
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