This is the little black knob you see off on the right under the V-shaped Can chute. This controls when the compressor is on and off and the fan down under the machine on the cooling sled.? It doe not control the fan that runs all the time continously inside the soda machine. Via the two wires on the back it turns the outlet on the left hand side off and on,? thus with the compressor plugged in there it turns the compressor off and on at the proper temperature. This thermostat works in conjunction with the Main Power cord (DLAA1295). Though made for a Dixe Narco Machine they can also be used on the Vendo's if you want to upgrade to a knob.