<VV> Head Light Problem...

[Mikeamauro at aol.com]

67 with parking lights wired to come on with head lights.
 
Changed the head light control switch about 2-months ago.  All was  fine 
until today: have no driver's side low beam with the dimmer switch calling  for 
low beam. When I press the dimmer switch, selecting high beams, all four  
headlights (as would be normal for high beam selection) come on. It would seem  the 
problem is not with the left side low beam, as it does illuminate with the  
high beam selection.
 
Pearls of wisdom, anyone?
 
Thanks,
Mike Mauro