Ok, now to research and see just what lights the light. I don't beleive it is like the 70's where the light only meant a "no charging" condition.
Take, for instance, the light on the left that looks like a radiator. When lit, it can mean the coolant level is low, it can also mean that the ECM has lost contact with or senses a failure in, the fan control module.

If you could monitor the system voltage while driving and see what happens to the voltage when the light is on and off, it would be a helluva clue.