Boxerworks.com

I just had a bout with that dang alternator. I’ve come to believe that a very high percentage of those little alternator gremlins are directly caused by those pesky little brushes. Those things have to be right or you’re going to get a light. (Red trouble light, that is)!

In my case, I finally determined that the brush holder was grounding out. I know, it didn’t make sense to me either? The only thing I could figure was that there was enough carbon dust from brush wear on the brush holder to actually create a path to ground. I removed the brush holder, and with a little compressed air and electrical cleaner, I got the alternator working like new.

Here’s a couple of other things to check that can create problems with those brushes.....

1) The little clock springs that push down on the brushes have to loop over the brush holder and push down on the brushes. They can become elongated and push on the side of the brush holder “instead” of the brushes. A pair of needle nose pliers will squeeze them back into shape.

2) The brushes should be installed in the right direction. The braided wires coming off the brushes can actually hang up on the brush holder if they’re in the wrong position and prevent the brushes from contacting the slip rings. The wires should be facing each other when the brushes are installed correctly.

If you’re chasing alternator gremlins, I recommend that you pull the alternator stator and thoroughly check those brushes. (You just can’t see that inside brush with the stator in place).
There’s 6 wires and 3 bolts to remove, and the stator pry’s out of a boss. To put it back, tighten the 3 mounting bolts only finger tight, then tap the stator back in the boss with a screwdriver handle. This makes it easy to get in straight and not tear anything up.

Yes, they can be a problem, but you should have had to live with the /2 brushes. That was 100 times worse and a real nightmare. Sometimes the brush and rotor wear were the first sign of a failing lower end.

I've been pulling my hair out on brushes lately too. On two separate bikes.

The brush housing is very difficult to remove. I ended up bending a spare 8mm wrench and wiggling it inside the alternator. It works but getting enough leverage to remove the nut can be tricky. Is there a special tool or trick to removing the housing other than my solution?

My soldering iron must not get hot enough to un-solder the old brushes off. Another frustration. Unless there a special trick to that as well?

Snowbum discusses brush holder removal at the top of this page:

http://bmwmotorcycletech.info/altbrushrotor.htm

Funny...a similar discussion going on at another vintage forum. I also had problems getting the inside nut off, even with a bent wrench. I finally gave up and will replace it when it is really needed.

Kurt in S.A.

I managed to get the nuts off with just a straight 8mm wrench. I found out that wasn't going to work for getting them back on. I used a fairly heavy pair of needle nose pliers to tighten them back up.

Those nuts were so difficult to get at, at first I tried desoldering the stator wires so I could remove the front cover. I found that was a two or three person job! The wires were put in the connectors then the connectors were crimped on the wires, then they were soldered. I think you'd have to be an octopus to get them apart!