1960 Volkswagen Beetle ALT

I put in a new alt but it only lasted about 2 weeks.
now the dash light is barley on, and the alt is putting out 19.04 to 19.23 volts at an idle.
and when more than a idle it goes down to about 18.33 volts when running.
other wise its over charging.
what to do?
the dash lite is brite before starting,
then is suposed to go out when the engine starts.
and it does but now the lite element barley glows orange.