This weekend the alternator light came on in my 84, miles from home while
my friend was driving (in fact she drove a long way with it on).  
We stopped and turned the engine off.  This
was a bad move since it would not restart - flat battery.  I traced the 
problem to the alternator brushes which are at the wear limit.  
Fortunately I had a spare battery which was charged enough to get the van 
started - just.  I have been meaning to wire it in as an aux with a 
solenoid for 
a while now but this experience makes me think twice, since if I had done
that, both batteries would have been dead and I would have been stuck!  The
advantage of an islolator is that even if the alternator dies you still have 
some power left...

PS.  where is best place to buy brushes from?

--
David Shepherdson