In this case, you are not checking ohmage per se, you are checking continuity. When switch is supposed to be off, meter should read "open". When it's supposed to be on, it reads some ohms or beeps. It does not make any difference how many ohms. You are not testing for proper ohms. Just to see if it has continuity. If it is passing current from one side of switch to the other. It is pretty easy to figure out which position is off and which position is on by mere observation of how it is mounted and operates. No reason to make this more complicated than it is. Continuity is usually tested with the component completely disconnected from any wires.
This switch is a lever operated, normally closed, momentary switch.
You can check it with the truck battery and bulb from truck. Don't need no stinking meter.
