Could it be that the low beam bulbs were installed inboard and the high beams outboard by accident? The metal bulb "cups" can be installed in the wrong locations.
I did that the 1st time.
FYI: The headlight dimmer switch has its own unique ground into the floor pan next to the switch itself.
The bulbs and cups are in the correct spots. Inner, 2 prong, outer 3 prong.
Does the floor switch get another ground besides being screwed into the floor??
