The alternator warning light comes on intermittently on this new (06)
truck, stays on for a few seconds, or a few minutes, goes on  & off
erratically like that for anywhere from a minute or two up to 10-20
minutes - then goes for long periods without coming on at all.  Happens
at idle as well as freeway speeds. So far I haven't had a dead battery
or any other problems, because it doesn't seem to last long enough to
affect the charge or the engine.   Sometimes if it's cruising at
freeway speed & the light is on, it will go off it I touch the
accelerator a little harder, so it does seem to be a charging problem,
rather than just a simple problem with the light.

This looks like one of those electrical things that's going to be hard
to find.  I'm wondering what to look for.

Any ideas?