This is a BRAND NEW Carrier/Bryant/Payne/ICP/Heil/Tempstar/Comfort Maker Heat Pump Defrost Sensor. The ICP Part # is 1173637 (found on the side of the sensor). Rated at L65F-33 . When a defrost sensor goes bad the heat pump will often turn to a solid block of ice (although this is not the only ice causing failure). Thanks for looking and good luck!
Sensors detect events or changes in their environment, and then relay the information to another device, typically a control board.