Voltage across an isolation switch

[Pwoffey]

I have a 500A isolation switch ( https://www.sherpa4x4.com.au/collect...olation-switch ) sitting between the positive cable from the solenoid box of my winch and the positive terminal of the battery. The winch works fine. Now say the Paj ignition is off and the winch controller is not connected. When I turn the isolation switch to the ON (closed) position there is 0 volts across the two terminals of the isolation switch. When I turn the isolation switch to the OFF (open) position there is 0.06 volts across the two terminals of the isolation switch. Is it normal to have any volts across an open isolation switch?

[Kingbrown]

It is quite feasible to read some voltage across open contacts when using a high impedance multimeter, even though you haven't got any load intentionally connected to the circuit.

The leakage of low voltage cables and connections will have a reasonably high resistance (lets say 2 Gig ohms) and the multimeter might have a high resistance of (say) 10 Meg ohms.

Simple voltage divider theory says the meter would read 59.7mV when the switch contacts are open. Just as you have seen with your measurement.

You can demonstrate what the leakage path does to your meter reading by touching one of the load connections of the circuit while also touching the body of the vehicle.

[Pwoffey]

Thanks for this, reassuring