I've got ice building up around the evaporator in my refrigerator (shocking). The thermistor seems to test out ok, but I'm a little less sure about the readings on the defrost thermostat (WR02X12592) and the defrost heater (WR02X12603).

The defrost thermostat seems to stay closed until about 140 Fahrenheit. It's closed when placed in ice water, and it's closed at room temperature. I had to put it in hot water to get it to open up. Is that the way this one should operate?

As for the heater, it's registering a resistance of 102 ohms. From what I can find that seems to be in normal range for defrost heaters... but I'm not sure if it's in normal range for this one.

Assuming all of this stuff is working, it sounds like the main control board is the only other likely culprit?

Any insights would be most appreciated.