GE Refrigerator quit cooling

GE Refrigerator Model dss25pfmdww suddenly quit cooling. Fans are blowing air, but it\'s cool, not cold. I looked at several troubleshooting discussions and they point toward the Temperature Thermistors and the Defrost Thermostat as most likely at fault. I put my VOM on the thermistors in the freezer and measured the resistance as I put them in ice water. Reading went from 10 K ohm at room temp to 14 K ohms in the ice water. They both  seem to be working. I also checked resistance through the Defrost Thermostat at room temp and after I put it in a working chest freezer for an hour. Thermostat never opened the circuit at either extreme. No resistance across it. What I thought that meant was that the thermostat was defective and should be replaced. I bought a new one and before I install it, I thought I should repeat the test on the new one. It also shows no resistance at room temp or after being frozen, same as the (defective) original. Am I missing some aspect of testing this? Is there another component that should be checked?