I need help, the generator lite came on and stays on and I am not sure why. The battery reads 12.7 volts with car off or on. Light stays on at any rpm. I then left a charger on battery overnight and it read 13.5 volts in morning. Started car and light still on. I am not sure what makes it come on. Thought it was when gen is trying to charge low battery. Meaning low battery would turn light on. How can I trouble shoot it?
Battery light is illuminated when the charge is leaving the battery faster than your generator can put a charge into the battery. Your car has a generator (alternators were introduced in 1963 if I remember correctly) so it is always charging (and drawing power to make electricity which is why the industry switched over to alternators). You have a set of two mechanical points that control if the battery is going to be charged or not (it is called a voltage regulator and it is mounted on your radiator core support). It balances the charge in the battery against the power the alternator produces.
I stated your generator is always cranking out power. That is true if it is working correctly. There are two brass contacts called brushes that ride on the armature's commutator (the part that spins) to conduct the electrical current generated out. If they are worn or the spring that pushes them into contact fails then your generator will not make power. This can be checked with a volt meter. All you need do is measure the voltage at the terminal as you raise the engines RPM. The voltage will rise with the increasing RPM (which is why your light glow yellow at idle instead of shining brightly as they do when the car is cruising).
If your generator is functioning (and odds favor this) then you will need to replace the voltage regulator. If not you can easily rebuild the generator yourself provided it doesn't also have a power steering pump attached to the back of the generator. With the power steering it can still be rebuilt but it is no longer easy. If it is the voltage regulator it should look like this on the radiator support with a bunch of wires attached to it. Be sure to note which wires go where before you remove them.
Sorry....typo....64 not 62, so it is an a-c generator, better known as an alternator! Any way, I got it working by messing with the points in the voltage regulator. I just exercised them a bit and the gen. lite went out. The alternator was putting out 15V.