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HI, I am new to this forum and need some advice or help with a new issue. Got a 2002 330xi 5 speed manual. Love it. But after not driving it for almost 2 weeks while being out of town, some very weird things started to happen when I got ack to drive it. First, I noticed the battery light stayed on the dash and the first few days I noticed it went away upon high acceleration with higher RPMs but then came back after RPMs stayed normal again. Then after about 3 days of doing that, even the higher RMP's wouldn't make that light go away. Then on the 4th or 5th day, I started it after work and before I drove off, I noticed weird things happening. Made clicking noises over my head like some sort of system was statically trying to turn on, then the abs and triangle with exclamation point lights went on. So I drove off on my way home and it started to lose power and eventually died. I ended up getting it jumped and it started but died again. did that three more times and I finally got it home being pulled by my girlfriend's suburban as it was close enough to begin with. So I took the alternator off and it tested good in three places that ran 2 to 3 different tests each time. The battery tested good at NAPA as it is a Mopar, 2 years old but it only had 220 cranking amps so I had it trickle charged and now it has 700. I put everything back together and it started right up but the same dash lights are still on. Anyone experienced this? Any help would be great.
 

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Sounds like you might need a new alternator.

Use a voltmeter on the battery, OR search for 'hidden menu' for the E46- it can tell you on the dash what the voltages are.

If you're below 13.7 or so when running, your alternator's not charging. Yes, checking connections and grounds is good,
but the alternator's the likely suspect given that the charge light is illuminated!

t
 

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Discussion Starter #3
Thank you for the reply. I thought so as well. I actually took the alternator out before anything else because I new for sure that its that. However it tested good at Oreillys, Autozone, and Napa Auto parts with each place testing it twice and even three times. That is why I am baffled. I guess I will check for alternator fuse and relay and after that I will test the charging system while it is running like you suggested to see if maybe it will test differently in the car versus by itself on the machine
 

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check the charging voltage on the battery like Toby said. that will basically tell you what's wrong in 1 step.
 

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Funny, I just let it sit for a day after the light went on and then it went away when I started it up again. Is it possible after reconnecting the battery after trickle charging out of the car at Napa, and then putting the alternator back together as well, does it need a few starts for it to register and reboot?
 

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Funny, I just let it sit for a day after the light went on and then it went away when I started it up again. Is it possible after reconnecting the battery after trickle charging out of the car at Napa, and then putting the alternator back together as well, does it need a few starts for it to register and reboot?
no that doesn't make sense. the alternator could be failing, the battery could be failing, the alternator could also be locking up or the belt could be slipping.

when batteries fail, they give off all sorts of random problems. so the battery could actually be the problem.
 

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Sounds like the alt to me.

But, check all your connections in the system first. Many here have tightened the cable clamps on the battery only to find the battery terminal is too small. Pull up on the clamp...wiggle it. Check under the +terminal under the hood to make sure it's tight and clean.

Still, though...sounds like the alt. It failed exactly as mine did--intermittently...and when it went 100% failure I was watching the voltage on my cluster as I drove home 40 miles at night on the battery only...as more and more warning lights came on. :)
 

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Discussion Starter #9
so it dies again today. charged the battery and all fine. but then same thing happened. the abs and brake lights started to flash while the battery light stayed on and then after driving on the re charged battery for 20 minutes it died again. My main question is this... Is it possible for the battery and alternator to pass the tests at auto parts stores, but still be bad enough to perform inside the car under full load?
 

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you need to check the voltage on the alternator while the car is running yourself. get a multimeter, a cheap one is like $6.
 

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The alternator is the likely culprit. Be advised that BMW sourced alternators from Bosch (yeah!) and Valeo ( ). They are not interchangeable without some work as the pulleys and the small connectors at the rear are different. The only way to tell which alternator is in the car is by removing the air filter box and using a flashlight and a mirror to read the label at the back of the alternator. Hopefully it’s a Bosch 120 amp alternator.

What typically goes wrong is the voltage regulator (VR) brushes. They wear out over time. If it’s a Bosch a new VR which includes brushes will be about $50 from FCPEuro. A Valeo VR will cost about $100. You’ll also need to replace item #3 in the link as it’ll crumble when you try to remove it.

 

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Sounds like the typical (what I preach a lot) alternator meeting the voltage output but the amperage output after heat soaking (placed on a hot engine and not on the bench at the parts store) is inadequate?
If it was here, I'd be doing a amperage test and an alternator ripple test. It's possible for an alternator to produce near correct voltage but not fully charge a battery back up owing to low amperage output as a result of bad rectifier diode pack.

Because we've been bit here before, a good known battery is the first step in diagnosing any charging issue.
The advice to check all the connections (alternator-starter-jump post-battery) is also a very good one.
 

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Also, use a digital volt meter and set it to alternating current (AC)!!! Put one lead in the jumper post under the red plastic cover under the hood, and the other lead on the engine. This will tell you if the alternator is producing AC. A friends of 300ZX was having electrical issues. I checked the voltage at the battery and it was all over the place. I checked the AC voltage at the battery and my meter read 32vac. He had to have the alternator replaced.
 

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Discussion Starter #14
Thank you all for that advice. It makes compete sense as I originally thought the voltage regulator was the culprit inside the alternator which is a BMW original it looks like (2002, 213k miles). I was going to check the alternator fuse and relay first after picking up my again good and fully charged battery and run those tests you all have suggested. I will report what I find and results.
 

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Discussion Starter #15
well it sounds like the battery is holding less and less charge. So it is tough to test the alternator or other components without a good battery so I will deal with that first and see how it goes.
 
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