With shore water disconnected open a faucet.If no water comes out the switch in off. If water comes out the switch is on.
That is assuming the pump works and there is water in the tank of course.
Clay (WA5NMR), Lee (Wife), Katie & Kelli (cats) Salli (dog).
Fixed domicile after 1 year of snowbirding and eleven years Full Timing in a 2004 Winnebago Sightseer 35N, Workhorse chassis, Honda Accord toad