The only real reason to put the probe in liquid is to create a buffer so the freezer will not "short cycle" (try to turn on within 2-3 minutes of when it shut off) when you open the top of the freezer. The johnson has an Anti-Short Cycle Delay parameter (see the instructions). Set it to 5 minutes. Set the diff to 1(really 2). Additionally put a small muffin fan in the freezer to circulate the air.