The simplest way to install a flood switch on a Fujitsu ARUH air handler is to land the N.O. contacts (Normally Open) of the flood switch to EXN 1 and 2 terminals. Then go into the function control settings of the wall control/thermostat (UTY-RNRUZ5 is the easiest to operate) and change function 46 to 02. Power cycle the system for 30 seconds, power up and test.