<VV> Gen /Fan light glows brighter as you rev the engine!!

[Barry Gershenfeld]

Well, not quite, since neither end of the GEN light is connected to
ground.  The bulb is connected to, and therefore showing the difference
between, the armature terminal of the generator, and the + side of the
electrical system.  I wanted to say "+ side of the battery", but actually
the + is picked up right out of the harness at the dashboard.  So, either
of these two things will cause the light to glow:

 - Generator voltage rising (unlikely, and would indicate bad regulator or
shorted Field wire; in addition your battery after being charged back up,
would start boiling out electrolyte)

 - 12V in the harness is "sagging".  Since the battery is a ways away from
this point, accessories can drag this voltage down a bit without affecting
the battery voltage.  It doesn't take much voltage for the bulb to glow
dimly.  This is by far the most common cause and you can see it because the
light gets brighter if you turn on the fan, wipers, etc.

Since the regulator connects "ARM" to "BAT" once the generator is running,
it effectively shorts out the light.  If those gen light wires actually ran
to that point, you wouldn't get this glow.  I think the ARM wire does.  But
not the BAT wire.