Answer Hello Will. The defrost timer is located behind the cover in the back of the refirgerator side. You can advance the timer until the unit shuts off. Once this is done, the heater should come on. If the heater does not come on, you will need to test the heater and thermostat and see if they are reading closed for continuity. Hope this helps. Read More... Answered by AppliancePartsPros.com | Wednesday, March 16, 2011