Author: steveng It takes time for your heater to acclimate and cool down to freezing temperatures. If you wish to use the “freezer test” to make sure your Xtreme Heater is operating properly, leave the heater in the freezer, or outside in freezing temperatures, for 30 to 45 minutes and then plug it in. The freeze spray method of testing is the most reliable method of confirming proper. Was this answer helpful ? Yes (0) / No (0) How can I tell if it is on? The light does not turn on when I plug it in, what’s wrong?