the headlight switch could be toast- there is a circuit breaker built inside as as over 30 odd years of working they eventullay get weak and trip out.
best way is to try and find another one--( have fun!! ) or do a relay upgrade to the headlights. using relays to power the main headlights off the alt. via a 30 amp fuse and triggering each relay for low and the other for high will take the heavy load off the main wiring and the headlight switch itself. there has been sebveral posts on this.
here is the one over at Dodge Charger-
http://www.dodgecharger.com/index.php/topic,168.0.html
any problems- email me- done this about 10 times!!!!