It is always a good idea to check the float switch before installation. The mechanism inside a float switch is straightforward. By raising the pivoting arm to the up position to simulate the switch floating in water is very much like pressing a switch to the 'on' position. It is possible to hear a mechanical 'click' on many float switches as the circuit is completed. Using a multimeter to check continuity will provide proof of the functionality of the switch. Attach each wire from the float switch to the terminals of the multimeter and raise the float switch. When it is in the 'up' position, the meter should show continuity, and by lowering the arm, the continuity should be broken.