Place the entire unit in the freezer. DO NOT LEAVE PLUGGED IN! Allow ONE HOUR for the unit to completely acclimate. Remove from the freezer and plug in. The heater should run for a minute or two, and then turn off.
Freeze Spray Method
Ensure the heater is plugged in and the light at the end of the cord is illuminated. The heater is equipped with two hexagon shaped testing ports that are located on the same side as the electrical cord. Place the spray nozzle just inside the small hole and spray a very short blast (1 second) of freeze spray. Wait about 30 seconds for the heater to turn on. Repeat if necessary. Each testing port should be tested.