The original switch in a ‘50 Chevy has only two positions, on and off. One terminal supplies the power and the other two are both hot when the switch is turned on. One as Kevin said, goes to the coil and also to the Amp meter. The other goes to the regulator.
This picture is the wiring diagram for a 50-51 from a 1948-1953 Chevrolet Shop Manual. I highlighted the paths to make it easier to see.
Phil Moderator, The Engine Shop, Interiors and Project Journals
1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes Project Journals Stovebolt Gallery Forum
