Alternator replacment, cost vs time

[oldskewel]

I have come to realize that the research effort to make decisions like this, combined with the helpless frustration when something would go wrong ends up being pretty costly.

So I almost always try to rebuild things like this myself with proper parts. It almost always comes out perfectly, and when it does not, it feels a lot better to have screwed it up myself than to have paid someone else to do it to me.

Yes it takes some skills and knowledge, but gaining those are a good investment.

[squidzilla]

Originally Posted by oldskewel

I have come to realize that the research effort to make decisions like this, combined with the helpless frustration when something would go wrong ends up being pretty costly.

So I almost always try to rebuild things like this myself with proper parts. It almost always comes out perfectly, and when it does not, it feels a lot better to have screwed it up myself than to have paid someone else to do it to me.

Yes it takes some skills and knowledge, but gaining those are a good investment.

You have rebuilt your own alternator? Wow. I did not that was even possible. Do you mind elaborating some on this? I am sure it is pretty involved, but I am still curious.

[oldskewel]

Originally Posted by squidzilla

You have rebuilt your own alternator? Wow. I did not that was even possible. Do you mind elaborating some on this? I am sure it is pretty involved, but I am still curious.

This thread follows the entire process, from debugging, onward for my '01 E53.

http://www.xoutpost.com/bmw-sav-foru...3-0i-01-a.html

In that thread the first and main thing I was looking for was any clues on diagnosis based on the intermittent working vs. non-working observations. I did not get any help there, but here is the answer - that absolutely can be a symptom of worn brushes, which is already the prime suspect in any alternator failure. Basically, as the shorter brush has worn just to the limit, it is right on the edge, and if contact is made, current flows and the alternator works. If no contact is made, no current, no charging. The slightest temperature changes, etc. can put you on either side of that fence.

I've rebuilt other alternators on my cars, as needed, with new bearings as well.

Some comments for the x5 here:
- It can be very confusing regarding compatibility between Bosch, Valeo, what year, what amperage, what you've actually got in your car. First thing I would recommend is ignore all that and dig into your car far enough to see EXACTLY what alternator you've got in there (Bosch vs. Valeo, and how many Amps should define it). Guaranteed to be faster than trying to figure it out via normal methods, which would only get you to a 60% chance of being right.

- The water cooled alternators are very different.

- For mine, and I expect many of the air-cooled alternators, worn out brushes are likely to be the only problem.

- When you've got it on the bench, it may be worthwhile to replace the bearings as well, if you have them in hand. I ended up buying a Valeo rebuild kit on eBay (supposedly covers an incredibly wide range of Valeo alternators) with new slip rings, bushings, and brushes, that I saved for doing a full rebuild the next time I get the alternator out. I could not wait that long at the time, so I just bought a new VR, which includes the brushes, and swapped it in.

There are many references throughout this list and other BMW lists on how to do the rebuild. Really not hard to do - about the same difficulty as R+R'ing the alternator itself.

Another post following that repair:
http://www.xoutpost.com/1071539-post7.html