I have a 1.18 volt drop from the battery voltage to the output side of the ignition switch.
What would the ohm be from the red wire to the blue wire out of the switch?
You need to know the current.
We can estimate current draw from most devices, or use a typical draw as a generalization.
Batteries are an exception. How much they will draw at any voltage depends on the battery condition. We can put a 14 Volt power supply across a charged battery and it will draw 0 amps. The same battery 20 % discharged with a 14 Volt power supply on it could draw 35 amps.
Few ohmmeters can read the resistances we're discussing here.
Most work by placing a small current through the system being tested.
And you can not measure voltage on a live system.
This is why we trace poor connections by putting current through a circuit and using voltage drops.
