Alternator - are these slip rings too worn to reuse?

[John Galt]

I pulled my alternator today, regulator brushes are way worn down, and the slip rings are heavily worn as well. See the picture below.


This alternator is from my 3.0i 2001 E53 with 200k miles.


Can I just put a new regulator on (maybe clean them up with a bit of sandpaper?), or do I need to replace the rings or the whole alternator?


Yes, I know it is very dirty, I'll get it totally clean if and when I put this one back on.

[oldskewel]

Looks OK to me. That Copper is pretty thick.

I would recommend using scotchbrite (the green scratchy stuff on some sponges) rather than sand paper to clean the surface. You want it to be smooth as well as clean.

Here are some pics from my 2001 3.0i with the 120A Valeo. Brushes wore out around 170k miles. Wanting to get it back on the road quickly, I bought a complete VR and swapped that in along with light cleaning of the slip rings. I saved the original VR and later replaced the brushes in it to keep as a spare.

Before and after Scotchbrite cleaning.

[cn90]

At 200K, it is time for new alternator.

Don't buy the junk at local auto parts store.

Stick to NEW Bosch or Valeo, it is about $220-$250 for a new unit.
I posted info in forum...

[andrewwynn]

As you can see only one side gets worn I'm planning to take wife's out and replace the brushes and swap the polarity of the slip ring power to basically double the life of the alternator.

When. I refurbished my slip rings, it was $325 for remanufactured unit or $20 for slip rings and brushes.


Sent from my iPhone using Tapatalk Pro

[cn90]

I have rebuilt alternator from scratch before.

At 200K, the bearings are at the end of their life.

It is much better with a new alternator.
I guess one can rebuild the old alternator (new brushes, which come with the new VR) and throw it in the trunk for emergency.

[andrewwynn]

I somehow missed the 200k miles. I agree with the idea that it might be time to make that one the spare. All depends how many cars you have at your disposal. I don't mind some more risky fixes because I have a few cars I can use when mine craps out.

Mine was at maybe 140,000 miles when I redid my slip rings. They were about as worn in the photo above but the failure at the time was brought to life by oil leaking into the alternator from a leaky oil filter.

[John Galt]

I got a new Valero and put it in, works perfect!

[andrewwynn]

Originally Posted by John Galt

I got a new Valero and put it in, works perfect!

Did you keep the old one? Specifically the VR? I want to make the modification I described above to swap the polarity of the field winding but it would be great to reduce the downtime by having a different VR to modify then swap it in . (Even better off I can pull off the miracle of swapping the VR in place!)

[cn90]

You can go to ebay and search "Valeo alternator brushes" and you will see on sales for $6.99, but you have solder the brushes in yourself.

There are some videos on youtube on how to solder.