Author: steveng You may have an earlier version of the Xtreme Heater, in which case the LED will light when the heater is activated, generating heat. Use freeze spray to test your heater for proper operation. Alternatively, the outlet you have plugged the heater into is not active. Try plugging in another electrical appliance, and check the circuit breakers on the boat and dock to make sure there is power to the outlet. Was this answer helpful ? Yes (0) / No (0) I put heater in the freezer or outside to test it and it is not turning on? Is there an on/off switch?