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Old 12-10-2015, 08:23 AM   #1
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Alternator Question for 2001 325I E46

Hi - I'm in need of an alternator and found one on e-bay for about $50 but it stated NO AIR DUCT 04/02, 3.0, A.T - what does this mean? Do I need the air duct. My alternator now is humming & is making noise which I think the bearings in the alternator are bad. Any guidance is helpful!
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Old 12-10-2015, 08:44 AM   #2
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You need to buy a proper replacement, $50 eBay alternators do not fit that description. If you go cheap prepare to replace it again quite soon.
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Old 12-10-2015, 08:47 AM   #3
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Go to and input your last 7 vin digits. You can look up the correct part and see what the duct looks like on your car.

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Old 12-10-2015, 10:05 AM   #4
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Skip the "eBay alternator" and avoid the headaches that come with the risk of junk parts.

There are some alternators that come with a plastic cover on the back with an air inlet.

Bosch w/ Lifetime Warranty:

After that, you have upper and lower air ducts that feed cool air to the unit.


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Old 12-11-2015, 07:05 AM   #5
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Alternator Question for 2001 325I E46

OP, you need to determine which alternator is in your car! BMW sourced alternators from Bosch and Valeo. You also need to determine the amperage of the alternator. To do this you'll need to remove the air cleaner box. Take a flashlight and a mirror and read the label on the back of the alternator. Hopefully it will say "Bosch." The amperage will most likely be 80 or 90 amps. Btw, the 2 brands of alternator's aren't interchangeable!! Why? The connectors are of different shapes and the pulleys are different.

Why are you swapping out the alternator?? The voltage regulator (VR) can be swapped out in an hour. A genuine Bosch VR will cost less than $50 from FCPEuro. Not sure about the Valeo. If you decide to change the VR (there's a DIY thread on how to do this) you should also change the cooling duct on the rear of the alternator as it will be very brittle.

Last edited by markusmarkus; 12-11-2015 at 07:09 AM.
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