Low Beams dead, Hi Beam Fine?

Floor Switch is bad. Headlight switch in the dash in regards to the headlights themselves only provides switched on power to the floor switch. Floor switch has 3 wires.

1 Power in from the headlight switch in the dash.
2 low beam out to lights
3 high beam out to lights

You have power from the dash switch because your high beams work. Your low beams dont work probably because the floor switch is bad, or the low beam wire on the switch is corroded. Being that the headlight dimmer is on the floor like that, there is usually a lot of dirt and water that gets into that connection.

If you had a bad ground from the headlights themselves to the car body, neither the high or low would work.