McDonnell & Miller FS4-3 Switch 30067439-890 Use a multimeter to check

Use a multimeter to check for coil continuity or verify the ohms resistance

but it is still best practice to handle the part by the ceramic base to prevent contamination and potential hot spots

Demineralized or distilled water with high specific resistance may require specialized high-sensitivity controls or chemical treatment to ensure the circuit completes reliably

The switch features a single-pole

McDonnell & Miller FS4-3 Switch 30067439-890 Use a multimeter to checkFor contractors requiring reliable system protection, the McDonnell & Miller FS4 3 (Part Number 114400) is a heavy duty general purpose liquid flow switch designed to monitor flow in heating, cooling, and water process lines. This 1" NPT unit features a single pole, double throw (SPDT) configuration, allowing you to easily integrate signal lights, alarms, motors, or burners into the control circuit. Engineered to operate at a max pressure of 160 PSI