Sponsored Links (Register now to hide all advertisements)
Technically, a circuit is only hot when the switch is on to complete the current path. The original Electro-Lock ignition switch breaks the circuit between the coil + terminal and the distributor so it controls the ground path to the breaker points. The breaker points control the coil function to get high tension induction for ignition which requires a timed opening sequence to get the pulsating DC current to make the coil induct that high tension voltage.
Modern ignition systems control the power side of the coil instead of the ground side. All of the pre-war and some post war Fords have a limited ignition switch function. When Ford started to use electric gauges for instrumentation, the ignition switch only controlled the ignition circuit and the instruments. Prior to that, the switch only controlled the ignition. Lighting and other electrical features had their own switches and fuses after Ford finally started using circuit protection.
Just to ADD, the original Ford ignition switches had a very low current carrying capability. I also don't recommend adding more loads to those early type switches. New circuits should have their own switches and circuit protection.