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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 07-18-2009, 12:36 AM
libmotors408 libmotors408 is offline
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Arrow Alternator Testing / Replacement Help!

Hey guys,

So my girls 02 bmw 330ci that we just got has some issues. She was driving on the freeway and the battery light came on. The stereo cut out and all cluster lights turned on. The car died on the freeway in the center lane. She managed to push it to the side and call tripple A.

She brought it to the BMW dealership where they reported that the battery was the wrong size and was fit for a Toyota Corolla.

I figured the alternator must have gone bad for the car to have the charging light come on.
Today I went to work on the car and got right in and started it right up! She was boggled that it started after the car was dead. Maybe they had charged the battery? I'm not really sure.

The car was running low on gas and we decided to drive it less than a mile to the gas station. It made it and we filled up with gas and came back.

I didn't check the battery size at this point but decided to dig right in to test the alternator. I then removed the intake hose with the air filter box to get to the alternator to test it. It is a BOSH (the more expensive one i believe) 120V alternator. On the back of the alternator there is a big BOLT and a Red power cable running from it. I put my multimeter postive lead on that and grounded the negative side. It read 0.00??

My questions are:

1) Is this the correct point to test for a 14.4V current?

2) If I did this correct and have readings for 0.00V how the **** did it make it to the gas station and there wasn't any battery light that came on?

3) Where can I get an NEW alternator for less than Kragen, they want 300 for the BOSH.

Thanks to all in advance!
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  #2  
Old 07-18-2009, 06:14 AM
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KrisL KrisL is offline
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First, get a new Autozone 49-DL battery. Drive for awhile and monitor the voltage. Second, test at the battery, not at the alternator. If you end up needing a new alternator, you can get them from buyautoparts.com for about $215.
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Old 07-18-2009, 07:52 AM
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Bucknekkid Bucknekkid is offline
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Won't disconnecting the (-) terminal at the battery while the car is running, indicate a bad or good alternator ?...Car running, disconnect (-) battery terminal, car dies=bad alternator...Car continues to run after disconnect of (-) battery terminal=good alternator...
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Old 07-18-2009, 08:16 AM
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KrisL KrisL is offline
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Quote:
Originally Posted by Bucknekkid View Post
Won't disconnecting the (-) terminal at the battery while the car is running, indicate a bad or good alternator ?...Car running, disconnect (-) battery terminal, car dies=bad alternator...Car continues to run after disconnect of (-) battery terminal=good alternator...
Although this is generally true, I wouldn't do this on a modern car... they're too sensitive to voltage spikes and dips... since the battery helps 'normalize' the voltage.
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Old 07-18-2009, 06:47 PM
libmotors408 libmotors408 is offline
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Ok, I had tested at the battery and it was reading 13.78 volts so it seems as if that's fine. I've never heard of testing the alternator at the battery?

Anyhow, we saw a battery at walmart for 75.00 bucks that fit the same group size. Do you think that it would be that much of a difference compared to an autozone battery? Besides the massive price difference!
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Old 07-18-2009, 07:39 PM
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Quote:
Originally Posted by libmotors408 View Post
Ok, I had tested at the battery and it was reading 13.78 volts so it seems as if that's fine. I've never heard of testing the alternator at the battery?

Anyhow, we saw a battery at walmart for 75.00 bucks that fit the same group size. Do you think that it would be that much of a difference compared to an autozone battery? Besides the massive price difference!
Massive price difference? I think the autozone is 79.99. (Autozone will tell you the 94-DLG is what your car needs at $129. The 49-DL at $79 fits great and offers even more CCA).
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Old 07-18-2009, 09:23 PM
jcourcoul jcourcoul is offline
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And should you choose to buy the "cheap WalMart solution" instead of the recommendations of Kris and the rest of the 'festers, just make sure what you buy has external venting and you plug the vent hole in the battery to the vent hose in the car. That is, unless you want to create a fire hazard in the sealed trunk of your vehicle.
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Old 07-19-2009, 09:50 AM
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49-DL is not $79.99 anymore(was $69.99 in 2007) but now it is $89.99 with the return of the old battery. Otherwise add another $12 to it.
If you buy the battery w/o returning the old one, your final bill will be around $110 after the tax. Not cheap but still lot better compared to the OEM one which is around $200 maybe more.

I would stay away from the Wal-Mart deal though. I never heard of Wal-Mart battery in a BMW
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  #9  
Old 07-19-2009, 09:41 PM
libmotors408 libmotors408 is offline
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ok thanks guys, my experience with european cars in general is very limited, but I'm planning on making a purchase in the near future for a BMW. I love the handling most of all and the heavy duty feel.

I still have a hard time believing that her car could have died on the freeway (NOTE: She was in bumper to bumper traffic when the battery light came on) due to the incorrect battery size. My understanding is that the battery is mainly just for starting the car. If the car is running and the alternator is good the car shouldn't shut off.

Thanks for all your help and I'm sure this will help out many others with alternator troubleshooting.

---------------------------------------------------------------------------------edited portion

Also I got a little more information from her on when and how it died and what happened afterwards. After the car died the tow truck guy tried to jump start it and it wouldnt start. Then the BMW dealership tried to jump it and it wouldn't start.

She than had the car towed back to her apartment and when I went to go work on the car it fired right up without jumping it and she didn't charge or replace the battery? This makes me wonder more what is wrong.

Last edited by libmotors408; 07-19-2009 at 09:56 PM.
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  #10  
Old 07-19-2009, 10:03 PM
jcourcoul jcourcoul is offline
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Since these cars have such extensive computerized control systems all over the place, they are very sensitive to electrical power supply. I would hazard that the new E90 platform is even more quirky, given that it is yet more computerized.

If the car seems to be ok now, I would suggest getting an OBD-II scan for any errant code left in the system, just for good measure. AutoZone has scanners they may lend, and if you bought the battery there, you can use that as leverage. Post back anything you find so the Supreme Geek Council can interpret and render a plan of action...
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Old 07-22-2009, 11:40 PM
libmotors408 libmotors408 is offline
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Update

So I purchased the 49-DL from autozone today and prepared to install it into the 2002 bmw 330ci.

Before installing I unlocked the car and all the lights lit up. Car seems fine at this point. I then tested the voltage at the battery and it was around 11.59 or so. I then tried starting the car. Car fired right up. I then decided to test the alternator again since I didn't know the BMW alternator had a special little hole area hidden behind the back of the battery for testing. (In my previous post i wasn't hitting the right spot and getting a 0 reading) The alternator was reading in the low 12's. I then replaced with the 49-DL as recommended and tested the battery. Battery was fine and then I tested the alternator again and it read in the 12's. I then decided for "****s and Giggles" to remove the negative on the battery post. Car was still running! WTF? I then tested the alternator again and it read the same results. I then tried again. The car shut off. I repeated the process a few times to confirm bad alternator and the car kept turning off after removing the negative cable.

I know KrisL said the following.

"irst, get a new Autozone 49-DL battery. Drive for awhile and monitor the voltage. Second, test at the battery, not at the alternator. If you end up needing a new alternator, you can get them from buyautoparts.com for about $215.
"

Is this alternator the correct one for replacing the BOSCH alternator on this 2002 bmw 330ci?

I just wanted to confirm what you guys think of the whole results. I'm ordering the bently manual tonight to replace the alternator. I was wondering if anyone had any experience changing it and if it required any "special" tools to complete the job.

Thanks for all the help.
Josh
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Old 07-23-2009, 09:18 PM
Lbert Lbert is offline
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Do not remove the battery cable(s) while the car is running. You are playing Russian roulette. If you think you have a problem now, you have seen nothing yet.

The battery has to be in good condition and fully charged to do an in car test of the alternator. The battery voltage has to be at least above 12.4V to properly test the alternator. Check the battery cables, cables to the alternator, and respective connectors. Make sure the connectors are clean and secure. If necessary, disconnect the cable connectors to clean the terminals. Also check your alternator belt is in good order and properly tensioned.

Start the car. Connect your multimeter across the battery terminals. At idle, you should get around 14V. Now have someone rev the rpm to about 2000 rpm for about 10 - 15 seconds while you take the voltage readings. Your lowest to highest reading should be 13.3V to 15.5V. Anything different, your alternator may need replacement.

The replacement is relatively straightforward. The Bentley manual is not absolutely necessary. Do a search. I am sure someone in the forum already did a write up already. I might do a write up on the project some day but not today.

Get your replacement alternator from your local auto supply store, e.g. Autozone. It will carry a lifetime warranty.

The tools required will be a selection of metric sockets, and a T50 torx bit is you have a hydraulic tensioner.
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  #13  
Old 07-24-2009, 03:14 AM
K.I.M.POSSIBLE K.I.M.POSSIBLE is offline
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FYI

12 volts from an alternater is not enough. The sole purpose of your alernatore is to carry the car's load while it is running and to keep the battery charged.

Therefore if you get a battery light while you are running the alternator is always the suspect not the battery.

You should always have 13 to 14.5 volts present at your battery terminals when the car is RUNNING and not less that 12 when it is off.

Also your dealer gave you stupid advice like most of them with that toyota corolla crap. The only diiference in batteries are the fitments, and CCA.( cold cranking amps ). They are all rated at the same voltage which is 12 with the minimum amount of amps to crank ANY car. Once the car is running its the ALternator that does all of the work NOT the battery unless there is a huge demand for current which at that time the CURRENT in the battery becomes a temporary supplement to the alternator so nothing starves.

Many time a car will die because the connections are not good and the alternator can not properly charge the battery when it is running and the supplemental "draw" os not there so it shuts off and will not restart. I belevie this may have been your issue OR you have an intermittent issue with your alternator but based on what you described, changing the battery will not be a permanent solution for you.
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Old 07-26-2009, 11:44 PM
libmotors408 libmotors408 is offline
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Torx bit to release tensioner?

Quote:
Originally Posted by Lbert View Post
Get your replacement alternator from your local auto supply store, e.g. Autozone. It will carry a lifetime warranty.

The tools required will be a selection of metric sockets, and a T50 torx bit is you have a hydraulic tensioner.
Does buyparts.com give the lifetime warranty on the alternator?

I'm not understanding what you mean by hydraulic tensioner? Do you mean the tensioner needs a T50 torx bit to release the tension?

Thanks all for your help, I'm going to try and take some pics of the car so someone else can get some help on this forum.
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Old 07-27-2009, 12:07 AM
libmotors408 libmotors408 is offline
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Just took a reading on the car with the battery connected and it was only putting out roughly 12 volts. It was funny though because i was starting to worry it wasn't the alternator because the tests were showing 14v at the beginning. After about 30 seconds the voltage reading started dropping. Time to replace the alternator! Will keep posting.
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Old 07-27-2009, 05:18 AM
sierrakilo99 sierrakilo99 is offline
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You'll need the large Torx bit to relieve the tensioner on the serpentine belt. Do yourself a favor and buy a set of Torx bits you'll need them to do most anything under the hood of these cars.
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Old 07-27-2009, 06:43 AM
3beemers 3beemers is offline
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Quote:
Originally Posted by libmotors408 View Post
Just took a reading on the car with the battery connected and it was only putting out roughly 12 volts. It was funny though because i was starting to worry it wasn't the alternator because the tests were showing 14v at the beginning. After about 30 seconds the voltage reading started dropping. Time to replace the alternator! Will keep posting.
Looks like the alternator was rendered useless when you ran the engine with the battery disconnected. Just like a dead battery, when you have someone give your battery a jump to start your engine, he is not supposed to take the jump right away until at least a few minutes to give your battery ample time to recover or at least turn the lights on. The purpose of which is to prevent overloading your alternator. So when you replaced your battery and removed one of the battery's connection while the engine is running....you were surprised that it still ran without the battery.... the possibility that you just killed your alternator at that point is very high.
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Old 07-27-2009, 04:46 PM
Lbert Lbert is offline
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Quote:
Originally Posted by libmotors408 View Post
Does buyparts.com give the lifetime warranty on the alternator?

I'm not understanding what you mean by hydraulic tensioner? Do you mean the tensioner needs a T50 torx bit to release the tension?

.
Either a mechanical or a hydraulic tensioner holds the alternator belt. Use a 16mm socket, I believe, to relieve the belt tension to the mechanical tensioner and a T50 torx for the hydraulic. Use a screwdriver to pry off the hydraulic tensioner black plastic cover to expose the T50 bolt underneath. Turning the tool clockwise relieves both tensioners.
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Old 07-27-2009, 04:50 PM
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Originally Posted by 3beemers View Post
Looks like the alternator was rendered useless when you ran the engine with the battery disconnected. Just like a dead battery, when you have someone give your battery a jump to start your engine, he is not supposed to take the jump right away until at least a few minutes to give your battery ample time to recover or at least turn the lights on. The purpose of which is to prevent overloading your alternator. So when you replaced your battery and removed one of the battery's connection while the engine is running....you were surprised that it still ran without the battery.... the possibility that you just killed your alternator at that point is very high.
I'm not buying that...
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Old 07-27-2009, 04:52 PM
Lbert Lbert is offline
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I forgot to answer whether buyparts.com gives a lifetime warranty. I do not know of any internet reseller that gives a lifetime warranty on anything. So the answer to your question is NO.
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Old 08-01-2009, 10:57 PM
libmotors408 libmotors408 is offline
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Hey great reply with the picture of the hydralic tensioner and mechanical. I started working on the car today and not really sure if it has the hydraulic tensioner or the mechanical. I removed the belt on the lower end with a 16mm offset box wrench. I want to remove the belt for the alternator but damn there isn't much space there. Do guys really remove it without taking out the fan coupler and shrouding?

Any ideas in removing the fan nut without having the 32mm wrench. I thought about trying to hit it with a flat head screwdriver and a hammer like someone said on another post. I wanna take some pictures and post them here because there isn't much of pictures of the way the engine bay looks.
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Old 08-30-2010, 10:56 PM
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Originally Posted by libmotors408 View Post
Hey great reply with the picture of the hydralic tensioner and mechanical.
FWIW, there are lots and lots of good pictures here ...
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