>In addition to checking the brushes, you also want to check the bearings.
>The rear bearing fails fairly frequently.  This causes the brushes to loose
>contact.  With the belt removed, check the pulley for side to side play.  If
>any, the bearings are wiped.
>

I encounterd bad bearings and a poor fit of the new bearing into the
alternator case. I was dismayed to find play even after I installed new
bearings so I made up the diff with thin sheet teflon. It worked well and
so far has lasted about 8k.

alistair