Next step in diagnosing my low beam driver's side headlight that won't work, which spade on the headlight switch powers up the low beam on the driver's side? Actually, is there a dedicated spade for it? For all I know, when you pull on the headlight switch, it powers up the headlights with just one spade.

On my 72, spade 56 on the headlight switch is what sends power to the headlight relay. Depending on which position the relay is in, the high beam or low beam will come on.

On my original relay, spade 56a was the low beam side and spade F was the high beam. Once I went to a new relay, the spades had different connect points.

Troubleshooting my headlights

Power for the headlight is a single wire (red w/white) out of the headlight switch to the headlight relay which controls high or low beam operation. From the relay there are 2 wires, 1 yellow and 1 white that go to the fuse panel. Each wire supplies power to 2 fuses. so the white wire provides power for the high beams via fuses 1 & 2. The yellow wire provides power for the low beams via fuses 3 & 4.

Good Luck

Jim