Johnson Ultima Automatic Bilge Pump Switch The Johnson Ultima Switch uses the patented Mirus field effect detector cells, producing micro-electrical fields that detect disruptions caused by water and fluids. The detector cells are totally sealed and are never in contact with the water, will not corrode, and are not affected by oil for foreign debris. Johnson Ultima Switch activates at a 2 fluid level and deactivates at a 34 fluid level. An eight second delay prevents false starts. The Ultima Swi