AP4303701. That is the part number for the defrost thermostat. I have checked four different thermostats using the method described by the techs on here. I checked for continuity while warm and while cold. Both conditions show an open circuit. I put the New thermostats in ice water and froze the ice water solid. Still shows open circuit. I am thinking that the thermostats are good and that the test is not good. Any ideas?

I feel the need to edit this post. The thermostats in question have spent several hours in the freezer. two of them are incased in glasses of water that is frozen solid. Those two have been in the freezer for two days. One has a thermometer in the glass of solid ice. The temp is below 15 degrees. it still shows an open circuit. Is there something that I do not know here?

The Temperature in the freezer is below ten degrees. I have several thermometers in the freezer to ensure an accurate reading. Three of the thermostats are not incased in ice. Two are. All of them are new. The ohm meter that I am using is fine. Like you said. I simply touch the probes together to check out the Ohm meter. The meter is fine. The freezer is cold enough and three of them are not the least bit wet. What the heck? Am I getting bad thermostats from the factory?

As it turns out the thermostat that Is installed and packed in un defrosted ice pack tests good. I decided to mimic the closed circuit by touching the wires together. Still no defrost. I guess I will have to get the $260 Circuit Board. Great. Thank you all for your help in this.