RE: Can the alternator fail and not light the red warning light on the dash?
Yes, it can, I had it happen to me about 18 months ago.  Worn brushes, no
output from the alternator, first warning was noticing that the fuel gauge
was indicating lower than it should have but that didn't register until I
died in the middle of the freeway.  Jumped to the aux battery and ran to my
destination, replaced regulator/brush pack and all was well.  I'll leave it
to someone else to trace out the circuit that allows this to happen but it
does.