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Subject: DIY: 1998 528i Bosch Alternator Rebuild for $30! Author: cn as CNN-090 : member since July, 2004 : 1088 posts Posted on: 2010-05-08 12:33:37

For 6-cylinder, you can rebuild your Bosch Alternator for $30!!!

I am gathering information for us 6-cylinder owners to tackle this Alternator Rebuild and do a quality job. So feel free to add info if you know of any good suppliers out there.

I called around, as it turns out many rebuilders in the US put in cheap Chinese bearings, no wonder the Bosch Alternators fail again in a few years. There are a few suppliers that sell rebuild parts to the majority of rebuilders throughout the US. And each rebuilder rebuilds the Alternator his way: you may get only new brushes, the old bearings may receive only grease (instead of being replaced). So when buying a rebuilt alternator, you are at the mercy of the rebuilders, whether it is sold at Autozone or online vendors.

Unlike other previous Bosch Alternator, the E39 Alternator uses a larger FRONT bearing 17x52x17mm type (this bearing takes a lot of pulling force from the drive belt, so they made it bigger to last longer), but this creates a different problem (see below).
Finding this larger bearing from a quality maker like SKF or Koyo is very very difficult (I have not found the supplier yet), so you may have to settle for Chinese bearing, which "might" be OK because Chinese bearings are a "hit or miss" thing, the Quality Control is spotty, some Chinese companies are very good and some very poor. And you don't want to take your alternator apart in 1-2 years to replace the front bearing. So if anyone knows a source for quality FRONT bearing, please chime in.

Reputable bearing makers are:
- INA
- F.A.G.
- SKF (USA)
- Timken (USA)
- Koyo (Japanese)
- Nachi (Japanese)

If you do the Rebuild yourself, you know you will do a quality job. The Bosch rebuilt alternators at Autozone are probably OK, but 99% of the time, they use cheap Chinese bearings, which may be OK but may not last as long as factory alternator.

Time to study the Typical Bosch Alternator anatomy! In fact most alternators, whether it is Honda, Toyota, or whatever car, have the similar setup. If you have not slept through your high-school Physics class, you probably understand how a typical alternator works.



Take you time and go through this excellent Rebuild DIY for a Bosch Alternator in a Range Rover, the E39 is slightly different and I will discuss below:
http://www.rangerovers.net/repairdetails/electrical/boschaltrepair.htm#steps

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[B]For 1998 528i (or similar models), the Alternator is:
- 120A Alternator
- Bosch 0 123 515 022
- BMW 1 432 986[/B]

A very good source for technical data is a company from the UK company Wood Auto:

http://woodauto.com/Unit.aspx?Man=BOSCH&Ref=0123515022[

All you need are:
1. Set of Carbon Brushes for $5:
- The whole Rectifier assembly is Bosch 1127319712 ($50 on ebay). If you buy this whole assembly, you don't need to buy the brushes.
- But a set of good carbon brushes is good enough because the rectifier rarely ever goes wrong. Brushes are Bosch 1127014028. Just undo the old brushes and install new brushes, you may have to solder them in the existing rectifier assembly.
Voltage12; Depth 3.9; Width 5.9; Length 16.
In the US, you can get the brushes from Wagner Alternator Supplier (PN W030-03K):
http://wagneralt.com/visions/wagner.asp?ID=232568

The bearings they carry are Chinese (they told me! Anyway this is what you get when you buy a rebuild Bosch Alternator!).

2. Small REAR Bearing 6203-2RS:
(2RS means "rubber seals" on both sides).
This bearing is very standard for Alternators: 17x40x12mm.
Search ebay, amazon etc. you will find some people selling SKF or Timken bearings.
Your local bearing store should have this.

3. Larger FRONT bearing: 17x52x17mm:
Bosch PN 1120905012 or B17-99:
You can easily find this for $9 at Bearings Direct:

http://www.bearingsdirect.com/store/index.php?l=product_detail&p=3485

If you don't mind using Chinese bearing for this part then go ahead, I still have trouble locating this particular bearing part using a reputable bearing makers mentioned above (SKF, Timken, Koyo, Nachi etc.), so any info on this particular bearing is appreciated!

CNN-090
1998 BMW 528i 5-speed 103K

• DIY: 1998 528i Bosch Alternator Rebuild for $30! (pic) (url) - CNN-090 2010-05-08 12:33:37 (6724 views)
  • having a hard time finding the rectifier for any cost - laszlo 2010-10-09 20:31:50 (2125 views)