GE Training Video: Testing and Replacing Thermistors in GE Refrigerators A great little training video from GE on testing and replacing the thermistors in their refrigerators. Well worth watching! This video gives a basic tutorial for diagnosing the electronic control board, or "muthaboard," used in GE refrigerators. Topics: Thermistor testing and replacing, including how to make proper splices. Fan testing. Compressor testing. Defrost system testing.