minor problem, not a real problem.
 

My alt. light is dimly lit @ idle, goes away when RPM's are increased
new battery, also changed voltage reg......no change.
Car does run fine and I have never had the battery go dead, so
why the light?

Don't worry about it. Probably enough resistance between the alternator and fusebox and dash wiring that the voltage is higher from the alternator to the alt bulb than through the system to the other side of the bulb. The easy fix is to put a diode on the small wire from the alternator, stripe on the end of the diode away from the alternator.