I checked for continuity with an OHM meter. Defrost thermostat was good. I then replaced it any way since the unit is old, the problem was the heater evaporator but this is the advice . Take it out of the unit and check for cracks or any visible damage. I checked mine it was giving me a good reading, but when I took it out of the unit I saw a tiny crack right on the tip and replaced it for a new one and fixed the problem and my return was hassle free. Thanks appliance parts pros.