The Emerson Electric Climate–White Rodgers 3F05-1 Adjustable Snap Disc Fan Control is a temperature-activated control designed to regulate fan operation in HVAC equipment. Adjustable from 90°F to 130°F with a 20°F differential, it works by automatically opening or closing electrical contacts in response to surface temperature changes. Commonly used in furnaces, unit heaters, and air h... https://www.partshnc.com/3f05-1-emerson-climate-white-rodgers-fanctrl-90130fcutin20f-dif