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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 12-28-2008, 07:36 PM   #1
vladvm
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Join Date: Jan 2008
Location: Toronto
Posts: 322
My Ride: 2002 325i
DIY - Alternator Disassembly

My alternator died..Car was driving fine. No drivability problem. then I felt the symptoms...

Symptoms:
1. Battery red dash light kept turning on/off intermittently
2. DSC/DTC/Brake light turn on intermittenlty
3. Battery red light stayed on, then all lights dim including headlights...
4. Car shuts down and died.

Checks:
1. I jumpstarted the car, but as soon as I removed the booster cable, car died...
2. I fully charged the battery, car started, drove around the block, but battery red dash light starts blinking intermittenty again...

The alternator was not charging my battery.

I wanted to see what is inside my alternator. It crapped out on me. Disclaimer: You are responsible for all your actions. This is for information purpose only.

First take out the alternator. There is a DIY on how to do this. If you have a 5-speed, you can easily take out the cooling fan and airbox to gain access. This can be done in 15min., no need to jack up the car. If you have auto, it will take longer.

FYI, I have a Bosch 120A.

ALTERNATOR DISASSEMBLY

Tools needed:
1. philips head screw driver
2. flat head screw driver
3. long 15mm socket
4. pliers


Here is the picture of the alternator.


1. To take off black plastic cover, take a philips screw driver and loosen one screw.


2. Use 15mm socket to loosen the 2 nuts. one of the nut is covered by black plastic, just pry it off to gain access.


3. Once cover is off, remove the voltage regulator using + screw driver (3 screws total).


4. Pull off the voltage regulator


5. Here is the voltage regulator.


6.Use - head screw driver and pliers to loosen the copper coils.




7. Use screw driver to loosen the diode assembly, and pull it off.


8. Here is the diode assembly.


9. Loosen the 4 screws to open the alternator casing.


10. Here are the bolts removed.


11. Pry open the top casing using the flat head screw driver.


12. Pry the bottom casing using the flat head.


13. Pull the coil out.


14. Here is the copper coil.


15. Here is the alternator internal without the coil


15. Reverse process to put it back together.
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Last edited by vladvm; 12-29-2008 at 10:37 AM.
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Old 12-28-2008, 08:55 PM   #2
Whammy
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Great thread!

I placed a request to move this to the correct forum. Thanks for posting this.
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Old 12-28-2008, 09:34 PM   #3
Raymond42262
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so, if your alternator went out, would you be able to rebuild it with available parts or is it better to just replace the whole thing?
great write up though !

Last edited by Raymond42262; 12-28-2008 at 09:35 PM. Reason: kudos
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Old 12-29-2008, 06:56 AM   #4
Whammy
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Quote:
Originally Posted by Raymond42262 View Post
so, if your alternator went out, would you be able to rebuild it with available parts or is it better to just replace the whole thing?
great write up though !
It is probably a matter of cost.
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Old 12-29-2008, 09:33 AM   #5
vladvm
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Join Date: Jan 2008
Location: Toronto
Posts: 322
My Ride: 2002 325i
Quote:
Originally Posted by Raymond42262 View Post
so, if your alternator went out, would you be able to rebuild it with available parts or is it better to just replace the whole thing?
great write up though !
I would think you can replace parts individually, but a rebuilt one would be better choice if you have money. Plus it will have the manufacturer warranty.

Taking apart the alternator would be a good way of clearing debris like dead leaves etc...

Personally, I am replacing the whole assembly.
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