Installing AC - Need help on Thermo SW

Installing AC for the first time on my 88 Jeep Comanche. Completed everything except the electrical. On the electrical diagrams it has a, "thermostat switch" and I am not talking about the radiator temp sensor. There is a thermostat built into the black heater fan box. Is this the temp sensor the schematics refer to? And exactly what is its function? Thanks for all of your help!

It's to keep the evaporator from icing.