heres my story outline version...

a. left ignition key on over weekend

b. did not realize ignition was left
on when i went to start engine monday
morning

c. used my 'quick start' jumper device(from
costco)to start engine

d. drove to work ok,couple miles, generator
light stayed off so charging seems to be
working. but still not enough juice to start
engine at end of day, so use quick start to
start again.

e. get home, charge the battery, install battery
and engine starts real easy. red generator
light flickers on and off, never solid... i
suspect fan belt is loose,so i try to tighten
with new shims...crank over engine, generator
light still flickers on and off

f. 3 wires on top of generator, two on trminal
lugs on top are tight...one towards the fan
housing on top of generator, maybe ground is
loose...i tighten it down and generator light
stays red....

g. any suggestions?...maybe the brushes? is there
a way to trouble shoot? the engine is in a
bus, so you know how hard it is to get to different parts....