On Mon, 7 May 2018 12:14:16 +0100, "Dan S. MacAbre"
wrote:

The washing machine packed in this morning. Filled up with water, and
then nothing. I expected I was going to need to replace the motor
brushes (although they're only about two years old), but they are still
quite long. I noticed that the commutator lands (or whatever you call
them) were blackened, and that the face of one of the brushes was quite
rough, like anthracite. I also remembered that last night, it was
making what I now realised was an arcing noise, and not a chattering
noise that I'd normally associate with the brushes getting too short.
Anyway, I cleaned them up, and it's working fine now, but I'm wondering
what caused it. Is one of the brushes malformed? Or has low spring
pressure? Or something else?

If you have replaced the brushes previously did you use like for like.

I never suspected that brushes were anything special, but they are
made to a tight spec in a lot of cases, and although the end purpose
is the same i.e taking current to copper, there are significant
differences in binders/ fillers used. I assume it's dependent on
rotational speed, current and insulating material.

I noticed that with my last washer, the brushes went, I replaced them
and a few weeks later the pump went.

Coincidence, or is manufacturing quality so good it can hit the
expected lifespan with accuracy on multiple components?

AB