Let’s talk about the defrost termination Klixon in a walk-in freezer - a small, "old-school" component that still does a big job. . Some call it outdated now that newer freezers use digital or on-demand defrost, but I still see these in the field all the time. . This Klixon is a temperature-activated switch that stays closed when the evaporator coil is cold. As frost melts during defrost, the coil warms up, and when the Klixon hits its cutoff temperature, it pops open and ends the defrost cycle